CFLAGS_COMMON_ARCH isn't available on all architectures

[KexyBiscuit]

Some build scripts in ABBS assumes CFLAGS_COMMON_ARCH exists¹, but that's not the case for every architecture.

autobuild4 supports 20 actual architectures now, but only 16 of them define CFLAGS_COMMON_ARCH.

• loongarch64.sh doesn't define CFLAGS_COMMON_ARCH, but defines CFLAGS_GCC_ARCH and CFLAGS_CLANG_ARCH separately, which should be outdated as of the writing, since LLVM 18 already supports LSX²³?
• loongson3.sh does the same thing as LA64, though I think Clang supports -mxgot⁴ for a long time?
• ppc64el.sh doesn't define CFLAGS_COMMON_ARCH but defines both CFLAGS_GCC_ARCH and CFLAGS_CLANG_ARCH as the exact same string.
• riscv64.sh has no CFLAGS* definition.

Should we...

• Make CFLAGS_COMMON_ARCH exist on every architecture, assigning at least some common flags to them for architectures like LoongArch 64 and Loongson 3?
• Remove inappropriate references to CFLAGS_COMMON_ARCH.

Also it might be time to review all these flags, I think this is a blocker of AOSC-Dev/aosc-os-abbs#5863.

Footnotes

1. https://github.com/AOSC-Archive/aosc-os-core/commit/2b5ecbaedd4c8cec8811d9692f1341ec63f82f54 ↩

2. https://releases.llvm.org/18.1.0/tools/clang/docs/ReleaseNotes.html#loongarch-support ↩

3. https://releases.llvm.org/18.1.0/tools/clang/docs/ClangCommandLineReference.html#cmdoption-clang-mlsx ↩

4. https://releases.llvm.org/18.1.0/tools/clang/docs/ClangCommandLineReference.html#cmdoption-clang-mxgot ↩

[KexyBiscuit]

For some history on this variable: in early 2017, when @MingcongBai add it to the build script, there were just 8 architectures supported by autobuild3, and all of them had CFLAGS_COMMON_ARCH defined¹.

Footnotes

1. https://github.com/AOSC-Archive/autobuild3/tree/7f56b10e51bef8b27dca12964312c0eee747d828/arch ↩