llvm-project

8fa29f84 - Reapply "[MC] Use a variant to hold MCCFIInstruction state (NFC)" (#170342)

Reapply "[MC] Use a variant to hold MCCFIInstruction state (NFC)" (#170342) This reverts commit 8217c6415ab76c2a0f06705100c76207cd1e6bc0. I asked Claude Sonnet 4.5 to hazard a guess at what was causing the buildbot failure, and it seems to have correctly pinned it on a bug in GCC7, although it didn't give a working fix. I worked out of a `gcc:7.4` docker container and moved code around until `MCDwarf.cpp.o` compiled without errors or warnings, so hopefully that's sufficient to fix the bot.