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.