[clang] [llvm] [Clang][Lexer] Reland "Detect SSE4.2 availability at runtime in fastParseASCIIIdentifier" (PR #175452)

[Petr Hosek via cfe-commits]

petrhosek wrote:

We started seeing assertion failures in Xcode's `libtool` on macOS when doing 2-stage LTO Clang build after this change:
```
FAILED: lib/libclangLex.a 
: && DYLD_LIBRARY_PATH=/Volumes/Work/s/w/ir/x/w/llvm_build/./lib "/Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool" -static -no_warning_for_no_symbols -o lib/libclangLex.a  tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/DependencyDirectivesScanner.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/HeaderMap.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/HeaderSearch.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/InitHeaderSearch.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/Lexer.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/LexHLSLRootSignature.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/LiteralSupport.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/MacroArgs.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/MacroInfo.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/ModuleMap.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/ModuleMapFile.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPCaching.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPCallbacks.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPConditionalDirectiveRecord.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPDirectives.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPExpressions.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPLexerChange.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPMacroExpansion.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/Pragma.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PreprocessingRecord.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/Preprocessor.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PreprocessorLexer.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/ScratchBuffer.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/TokenConcatenation.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/TokenLexer.cpp.o && cd /Volumes/Work/s/w/ir/x/w/llvm_build/tools/clang/stage2-bins/tools/clang/lib/Lex && touch /Volumes/Work/s/w/ir/x/w/llvm_build/tools/clang/stage2-bins/./lib/libclangLex.a
Assertion failed: (isa<GlobalAlias>(GV)), function parseSymbols, file LTOModule.cpp, line 614.
/bin/sh: line 1: 37655 Abort trap: 6           DYLD_LIBRARY_PATH=/Volumes/Work/s/w/ir/x/w/llvm_build/./lib "/Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool" -static -no_warning_for_no_symbols -o lib/libclangLex.a tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/DependencyDirectivesScanner.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/HeaderMap.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/HeaderSearch.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/InitHeaderSearch.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/Lexer.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/LexHLSLRootSignature.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/LiteralSupport.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/MacroArgs.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/MacroInfo.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/ModuleMap.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/ModuleMapFile.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPCaching.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPCallbacks.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPConditionalDirectiveRecord.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPDirectives.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPExpressions.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPLexerChange.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PPMacroExpansion.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/Pragma.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PreprocessingRecord.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/Preprocessor.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/PreprocessorLexer.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/ScratchBuffer.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/TokenConcatenation.cpp.o tools/clang/lib/Lex/CMakeFiles/obj.clangLex.dir/TokenLexer.cpp.o
```

https://github.com/llvm/llvm-project/pull/175452