fix(llvm,llvm20): add azurelinux-specific triple to clang default fallback list

[tobiasb-ms]

Summary

Add x86_64-azurelinux-linux and aarch64-azurelinux-linux to clang's GCC installation fallback triple list in Gnu.cpp. This allows clang-based tools (clang-tidy, clang++, etc.) to discover GCC headers installed under the Azure Linux vendor-specific triple without requiring explicit --gcc-toolchain or -isystem flags.

Problem

clang's GCC installation detector searches a hardcoded list of vendor triples when locating the system GCC. Azure Linux uses {arch}-azurelinux-linux as its vendor triple (visible in /usr/lib/gcc/x86_64-azurelinux-linux/), but this wasn't in clang's fallback list. As a result, clang-tidy and other tools failed to find <cstdio> and other libstdc++ headers, causing %check failures in packages like meson that run clang-tidy during their test suites.

Fixes: Bug #20333 — [Nightly Break] meson: %check fails - clang-tidy unit tests cannot find <cstdio>

Related: Bug #20284, Bug #20324 (ROCm/clang toolchain gap — same root cause)

Testing

• Both llvm and llvm20 built successfully on ControlTower
• meson built successfully (including %check) with the updated llvm in the local buildroot
• Patch includes upstream-style test cases in clang/test/Driver/linux-ld.c

Changes

• llvm (21.x): add patch, bump release
• llvm20: add same patch, bump release

[Copilot]

Pull request overview

This PR updates the Azure Linux llvm and llvm20 components to ensure clang can discover GCC installs under Azure Linux’s vendor triple ({arch}-azurelinux-linux) by patching clang’s GCC-install fallback triple lists and adding upstream-style driver tests.

Changes:

• Add x86_64-azurelinux-linux and aarch64-azurelinux-linux to clang’s fallback triple detection in Gnu.cpp.
• Add clang driver tests (and minimal test sysroot inputs) to validate the fallback detection works for both x86_64 and aarch64.
• Bump rendered spec releases / lock fingerprints for both llvm and llvm20 to reflect the change.

Reviewed changes

Copilot reviewed 8 out of 10 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
base/comps/llvm/llvm.comp.toml	Adds patch overlay + manual patch application hook for llvm.
base/comps/llvm/0001-Clang-Add-azurelinux-to-fallback-triples.patch	Carries clang triple/test changes as a patch source.
base/comps/llvm20/llvm20.comp.toml	Adds the same patch overlay + manual application hook for llvm20.
base/comps/llvm20/0001-Clang-Add-azurelinux-to-fallback-triples.patch	Carries clang triple/test changes as a patch source for llvm20.
specs/l/llvm/llvm.spec	Rendered spec update: adds Patch2202, applies it, bumps release/changelog.
specs/l/llvm/0001-Clang-Add-azurelinux-to-fallback-triples.patch	Rendered copy of the patch under specs/.
specs/l/llvm20/llvm20.spec	Rendered spec update: adds Patch2202, applies it, bumps release/changelog.
specs/l/llvm20/0001-Clang-Add-azurelinux-to-fallback-triples.patch	Rendered copy of the patch under specs/.
locks/llvm.lock	Updates input fingerprint after component change.
locks/llvm20.lock	Updates input fingerprint after component change.

[ddstreetmicrosoft]

I'm not thrilled by this...as the comment just a few lines above says, "Please don't add more elements to *Triples". But digging into how to avoid this ourselves probably isn't appropriate or worth the time (trying to get upstream to fix the need for this hardcoded list is the right way to avoid this).

So this looks ok to me.

[tobiasb-ms]

Agree, though options are limited. I do think that the Fedora change https://src.fedoraproject.org/rpms/llvm/c/879a14ed99a04dbfca4e3c3c57abb33b61e1a3dc?branch=rawhide will mostly obviate the need for this as it will install the config files that have these triples with clang-libs rather than clang. But this fallback is probably good to have anyway.

FWIW, I've also submitted a PR to LLVM: llvm/llvm-project#200894, but not traction thus far (and as the you suggest, based on the comment, I wouldn't be surprised if they reject it).