s390x-linux-gnu-gcc: error: unrecognized command-line option '-mno-omit-leaf-frame-pointer'

When compiling for `s390x-linux-gnu-gcc` using Rust version `2026-08-07 for version 1.99.0-nightly (84b36a78a 2026-08-06)` I get this error:

```
[53](https://github.com/zip-rs/zip2/actions/runs/31203028685/job/92965869807#step:12:154)
warning: zstd-sys@2.0.16+zstd.1.5.7: s390x-linux-gnu-gcc: error: unrecognized command-line option '-mno-omit-leaf-frame-pointer'; did you mean '-fno-omit-frame-pointer'?
warning: zstd-sys@2.0.16+zstd.1.5.7: ToolExecError: command did not execute successfully (status code exit status: 1): LC_ALL="C" "s390x-linux-gnu-gcc" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-gdwarf-4" "-fno-omit-frame-pointer" "-mno-omit-leaf-frame-pointer" "-I" "zstd/lib/" "-I" "zstd/lib/common" "-w" "-fvisibility=hidden" "-ffunction-sections" "-fdata-sections" "-fmerge-all-constants" "-DZSTD_LIB_DEPRECATED=0" "-DXXH_PRIVATE_API=" "-DZSTDLIB_VISIBILITY=" "-DZSTDERRORLIB_VISIBILITY=" "-o" "/home/runner/work/zip2/zip2/target/miri/s390x-unknown-linux-gnu/debug/build/zstd-sys/10cbbb9d06aad04a/out/44ff4c55aa9e5133-debug.o" "-c" "zstd/lib/common/debug.c"cargo:rerun-if-env-changed=CC_s390x-unknown-linux-gnu
```

Start by reproducing the s390x-unknown-linux-gnu build and tracing how zstd-sys assembles compiler flags for the failing zstd/lib/common/debug.c compilation. Done means the s390x build completes without passing the unsupported -mno-omit-leaf-frame-pointer option to s390x-linux-gnu-gcc.

Written by the indexing model from the issue text.