rust: need a way to pass ldflags to rustc?

Maintainer: @lu-zero @1715173329
Environment: x86_64, glibc

Description:

I wanted to compile einat , but somehow rustc cannot found libintl at the end.

I have tried everything

TARGET_CFLAGS += -Xlinker -rpath=$(STAGING_DIR)/usr/lib/libintl-full/lib
or
TARGET_LDFLAGS += -L$(STAGING_DIR)/usr/lib/libintl-full/lib -lintl
or
export LD_LIBRARY_PATH=$(STAGING_DIR)/usr/lib/libintl-full/lib

but rustc still didn't picked it up.

   Compiling einat v0.1.2 (/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3)
     Running `rustc --crate-name build_script_build --edition=2021 build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off -C overflow-checks=on --cfg 'feature="default"' --cfg 'feature="ipv6"' -C metadata=13037c25982734ec -C extra-filename=-13037c25982734ec --out-dir /home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/einat-13037c25982734ec -C linker=x86_64-openwrt-linux-gnu-gcc -C strip=symbols -L dependency=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps --extern libbpf_cargo=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblibbpf_cargo-fc7173ecf7072a22.rlib -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/libbpf-sys-de20753a55c71e06/out -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release -L native=/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/vsprintf-f6a1be3b8a629995/out`
error: linking with `x86_64-openwrt-linux-gnu-gcc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/bin:/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/bin:/home/user/works/openwrt/staging_dir/hostpkg/bin:/home/user/works/openwrt/staging_dir/toolchain-x86_64_gcc-14.1.0_glibc/bin:/home/user/works/openwrt/staging_dir/toolchain-x86_64_gcc-14.1.0_glibc/bin:/home/user/works/openwrt/staging_dir/host/bin:/home/user/works/openwrt/staging_dir/host/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" VSLANG="1033" "x86_64-openwrt-linux-gnu-gcc" "-m64" "/home/user/works/openwrt/tmp/rustca9rJSt/symbols.o" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/einat-13037c25982734ec/build_script_build-13037c25982734ec.build_script_build.900026c213c08482-cgu.0.rcgu.o" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/einat-13037c25982734ec/build_script_build-13037c25982734ec.2kuwii56gzittnew.rcgu.o" "-Wl,--as-needed" "-L" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps" "-L" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/libbpf-sys-de20753a55c71e06/out" "-L" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps" "-L" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release" "-L" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-L" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/vsprintf-f6a1be3b8a629995/out" "-L" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblibbpf_cargo-fc7173ecf7072a22.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libcargo_metadata-77b698b469ccad23.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libserde_json-d18e1952940c9d6c.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libitoa-c99bf860a1243733.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libryu-42733ab1749368f9.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libthiserror-aa231274481bae73.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libcargo_platform-c20f7cad56b30019.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libcamino-a1fd712e042bd596.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libmemmap2-73fca818d05ca4c9.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblibbpf_rs-12af648727bedc4e.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libvsprintf-52f5d1afc74d566c.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblibc-a50be116079b6680.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblibbpf_sys-6ce4fe8ed806fc57.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libsemver-d9af4a6bbaa40b09.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libserde-73abfa3b10e52ca3.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libregex-662c0e78adcebbf3.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libregex_automata-e8e6e085a55c8ab3.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libregex_syntax-f1d457fe75bcbfd6.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libtempfile-e4833a2ad6c4f429.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libfastrand-906c084e5ef6039e.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/librustix-4d3b20d2716f8231.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libbitflags-3a495cf5bbfede0b.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblinux_raw_sys-ba02cfb0a81adfba.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libcfg_if-1c8851ce38e8a7c1.rlib" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/libanyhow-0deb8dd3c263e7fc.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-18d1c84127d04dc5.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libpanic_unwind-bc53c6e5d5f4111f.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libobject-a79bc22e6ae9ee83.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libmemchr-9c256084533d6dad.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libaddr2line-e53b44d64d10bb35.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libgimli-9d0b3274a5b15e82.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_demangle-b0fb619b58a6601a.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd_detect-1319f451087d6793.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libhashbrown-e7ba5787d3fb181b.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_alloc-e23167ed65317fed.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libminiz_oxide-52af0786d05d61a5.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libadler-28f9d348427e8d43.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunwind-689892118ddcc60e.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcfg_if-a1f86f0be6e775e6.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-cbc93ea126f55c98.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-390f90785cbfdde3.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_core-aded7817e4ea9283.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-6c16e1294e732b84.rlib" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-a8a94ae78107d089.rlib" "-Wl,-Bdynamic" "-lelf" "-lz" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/einat-13037c25982734ec/build_script_build-13037c25982734ec" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-Wl,--strip-all" "-nodefaultlibs"
  = note: /home/user/works/openwrt/staging_dir/toolchain-x86_64_gcc-14.1.0_glibc/lib/gcc/x86_64-openwrt-linux-gnu/14.1.0/../../../../x86_64-openwrt-linux-gnu/bin/ld: warning: libintl.so.8, needed by /home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/usr/lib/libelf.so, not found (try using -rpath or -rpath-link)
          /home/user/works/openwrt/staging_dir/toolchain-x86_64_gcc-14.1.0_glibc/lib/gcc/x86_64-openwrt-linux-gnu/14.1.0/../../../../x86_64-openwrt-linux-gnu/bin/ld: /home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/usr/lib/libelf.so: undefined reference to `libintl_dgettext'
          collect2: error: ld returned 1 exit status
          
  = note: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
  = note: use the `-l` flag to specify native libraries to link
  = note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#rustc-link-lib)

error: could not compile `einat` (build script) due to 1 previous error

Caused by:
  process didn't exit successfully: `rustc --crate-name build_script_build --edition=2021 build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off -C overflow-checks=on --cfg 'feature="default"' --cfg 'feature="ipv6"' -C metadata=13037c25982734ec -C extra-filename=-13037c25982734ec --out-dir /home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/einat-13037c25982734ec -C linker=x86_64-openwrt-linux-gnu-gcc -C strip=symbols -L dependency=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps --extern libbpf_cargo=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps/liblibbpf_cargo-fc7173ecf7072a22.rlib -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/libbpf-sys-de20753a55c71e06/out -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/deps -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release -L native=/home/user/works/openwrt/staging_dir/target-x86_64_glibc_custom/host/lib/rustlib/x86_64-unknown-linux-gnu/lib -L native=/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target/release/build/vsprintf-f6a1be3b8a629995/out` (exit status: 1)
warning: build failed, waiting for other jobs to finish...
error: failed to compile `einat v0.1.2 (/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3)`, intermediate artifacts can be found at `/home/user/works/openwrt/build_dir/target-x86_64_glibc_custom/einat-ebpf-0.1.3/target`.
To reuse those artifacts with a future compilation, set the environment variable `CARGO_TARGET_DIR` to that path.

Start with the Rust build invocation shown in the issue and the package's build.rs, then review CONTRIBUTING.md for the repository's package-build conventions. Determine where linker flags are assembled and how a package can pass them to rustc; done means the einat build can link libintl without manually exporting environment variables.