Link to shared libraries normally or set RPATH, instead of relying on LD_LIBRARY_PATH

Expected Behaviour

Binaries should run without requring any magical environment variables.

Example & Steps To Reproduce

The examples are not directly runnable (i.e. not using cargo run) due to unnecessary LD_LIBRARY_PATH shenanigans:

$ cargo build -p example-runner-wgpu
$ target/debug/example-runner-wgpu

thread 'main' panicked at crates/spirv-builder/src/lib.rs:745:9:
Could not find librustc_codegen_spirv.so in library path
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

This happens because you're looking for that file by manually parsing the LD_LIBRARY_PATH environment variable. It's my understanding that this lookup is only performed so the location of that file can be passed to a rustc invocation later, so it doesn't even make sense to look this up in LD_LIBRARY_PATH.

Upon manually setting LD_LIBRARY_PATH:

$ LD_LIBRARY_PATH=$PWD/target/debug ./target/debug/example-runner-wgpu

thread 'main' panicked at examples/runners/wgpu/src/graphics.rs:467:49:
called `Result::unwrap()` on an `Err` value: Os(OsError { line: 81, file: "/home/max/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/winit-0.30.7/src/platform_impl/linux/wayland/event_loop/mod.rs", error: WaylandError(Connection(NoWaylandLib)) })
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Regardless of the mechanism that's used to find librustc_codegen_spirv.so, it should not be necessary that these graphics libraries are discovered through LD_LIBRARY_PATH at all. Via RUSTFLAGS, one can configure the output binary's RPATH:

--- a/default.nix
+++ b/default.nix
@@ -14,7 +14,7 @@ in with pkgs; stdenv.mkDerivation rec {
   nativeBuildInputs = [ rustup ];

   # Runtime dependencies (for the example runners).
-  LD_LIBRARY_PATH = with xorg; lib.makeLibraryPath [
+  env.RUSTFLAGS = "-C link-arg=-Wl,-rpath,${with xorg; lib.makeLibraryPath [
     vulkan-loader

     # NOTE(eddyb) winit really wants `libxkbcommon` on Wayland for some reason
@@ -22,5 +22,5 @@ in with pkgs; stdenv.mkDerivation rec {
     wayland libxkbcommon

     libX11 libXcursor libXi libXrandr
-  ];
+  ]}";
 }

$ cargo build -p example-runner-wgpu
$ patchelf --print-rpath target/debug/example-runner-wgpu | tr : \\n
/nix/store/pkzygdv7p08cma6q6zbarprkmdbgqn6m-vulkan-loader-1.4.313.0/lib
/nix/store/h64w118vqfw706px8ranz6cx07ki06jl-wayland-1.23.1/lib
/nix/store/dxh4x7x96lfadv500bdw3m2b3h4a3vwa-libxkbcommon-1.10.0/lib
/nix/store/26c0x3gh2g5dpczvjxgjzn0mc22zxpjz-libX11-1.8.12/lib
/nix/store/2dv3na4hkiq5l3af3a25wb5a390grr2x-libXcursor-1.2.3/lib
/nix/store/mnyka5w2k0jbfnfzrazhgwrhk6nnldnq-libXi-1.8.2/lib
/nix/store/22da37glz0r7vs536nj9n6h56kh1lr7m-libXrandr-1.5.4/lib
/home/max/Projects/rust-gpu/outputs/out/lib
/nix/store/q4wq65gl3r8fy746v9bbwgx4gzn0r2kl-glibc-2.40-66/lib
/nix/store/l7d6vwajpfvgsd3j4cr25imd1mzb7d1d-gcc-14.3.0-lib/lib

The best option would be to actually link the binaries to the shared libraries like normal. For example, ash supports this through an optional feature. wgpu does not seem to expose it.

System Info

• Rust: rustc 1.89.0-nightly (be19eda0d 2025-06-22)
• OS: NixOS 25.11.20250627.30e2e28

Reproduce with cargo build -p example-runner-wgpu and inspect the shared-library lookup around crates/spirv-builder/src/lib.rs:745; compare it with the runtime settings in default.nix and the failure in examples/runners/wgpu/src/graphics.rs. Done means the example runner starts without manually setting LD_LIBRARY_PATH, using normal shared-library linking or an appropriate RPATH.