rustc: un-mark broken for LLVM stdenv

[RossComputerGuy]

Things done

Essentially reverts #375267 since #330037 fixes it.

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

---

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[alyssais]

Please include the explanation in the commit message, not just the PR body (ideally with commit hashes rather than PR numbers so they can be looked up locally).

[RossComputerGuy]

Done

[ccicnce113424]

Build still fails.
nix-build -A pkgsLLVM.rustc

error: builder for '/nix/store/yrrdvhciy957k1niz4n0nmyls8xws2mm-x86_64-unknown-linux-gnu-rustc-1.88.0.drv' failed with exit code 1;
       last 25 log lines:
       >    Compiling same-file v1.0.6
       >    Compiling log v0.4.22
       >    Compiling generic-array v0.14.7
       >    Compiling semver v1.0.23
       > error: failed to run custom build command for `proc-macro2 v1.0.89`
       >
       > Caused by:
       >   process didn't exit successfully: `/build/rustc-1.88.0-src/build/bootstrap/debug/build/proc-macro2-1d0ab93154a598ed/build-script-build` (exit status: 127)
       >   --- stderr
       >   /build/rustc-1.88.0-src/build/bootstrap/debug/build/proc-macro2-1d0ab93154a598ed/build-script-build: error while loading shared libraries: libunwind.so.1: cannot open shared object file: No such file or directory
       > warning: build failed, waiting for other jobs to finish...
       > error: failed to run custom build command for `crossbeam-utils v0.8.20`
       >
       > Caused by:
       >   process didn't exit successfully: `/build/rustc-1.88.0-src/build/bootstrap/debug/build/crossbeam-utils-4f842ad50ef35632/build-script-build` (exit status: 127)
       >   --- stderr
       >   /build/rustc-1.88.0-src/build/bootstrap/debug/build/crossbeam-utils-4f842ad50ef35632/build-script-build: error while loading shared libraries: libunwind.so.1: cannot open shared object file: No such file or directory
       > error: failed to run custom build command for `serde v1.0.215`
       >
       > Caused by:
       >   process didn't exit successfully: `/build/rustc-1.88.0-src/build/bootstrap/debug/build/serde-e81ee783027b48a5/build-script-build` (exit status: 127)
       >   --- stderr
       >   /build/rustc-1.88.0-src/build/bootstrap/debug/build/serde-e81ee783027b48a5/build-script-build: error while loading shared libraries: libunwind.so.1: cannot open shared object file: No such file or directory
       > failed to run: /nix/store/kg6psfcz4vjcvv8bpyvw422vrndrcq50-cargo-1.88.0/bin/cargo build --manifest-path /build/rustc-1.88.0-src/src/bootstrap/Cargo.toml -Zroot-dir=/build/rustc-1.88.0-src --frozen
       > Build completed unsuccessfully in 0:00:02
       For full logs, run 'nix log /nix/store/yrrdvhciy957k1niz4n0nmyls8xws2mm-x86_64-unknown-linux-gnu-rustc-1.88.0.drv'.

[nixpkgs-ci]

Successfully created backport PR for release-25.05:

• [Backport release-25.05] rustc: un-mark broken for LLVM stdenv #429811