Zigbuild linking fails with nightly (2025-03-09) on x64 linux

[scootermon]

rustc now adds -znostart-stop-gc to the linker args automatically for x64 linux targets.
See: rust-lang/rust#137685

Zig doesn't support this arg so it fails with note: error: unsupported linker extension flag: -z nostart-stop-gc.

A workaround for this is to explicitly set RUSTFLAGS="-Zlinker-features=-lld".

[messense]

Failed to reproduce it in https://github.com/rust-cross/cargo-zigbuild/actions/runs/13766899068/job/38611411963?pr=325 with nightly 2025-03-11?

[scootermon]

For reference, I ran the CI specifically with 2025-03-09 and was able to reproduce it: https://github.com/inomotech-foss/cargo-zigbuild/actions/runs/13805814897/job/38616290883

I haven't checked yet what's changed in the new nightly version.

[Kobzol]

We only pass this flag when we tell the linker to link with LLD (as we expect the linker to be a GCC/clang-like compiler driver). Seems like that doesn't really work if the linker is actually Zig.

[Kobzol]

#334 should resolve this.