[clang] [llvm] [Clang][CodeGen][X86] Fix crash on __int128 bit-field access units (PR #216777)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

> > No against reverting, but is the problem just missing a `-fclang-abi-compat=23`? I think it's also ok to commit a seperate patch for it.
> 
> +1; I think a revert is fine to give breathing room but I think fixing it forward to give an ABI compat flag is also fine if done quickly enough

https://github.com/llvm/llvm-project/pull/220901
 
> Are there bots that should have reported that breakage? The only report that I can see is for https://lab.llvm.org/buildbot/#/builders/190/builds/48978

We (Arm) are about to add a ClangIR bot - it's already running downstream and we are in the process of connecting it to LLVM's master bot. For that to happen, the bot needs to be 🟢 and stable (to minimise the changes to llvm-zorg). 

If that's OK with you, please accept and land my reverting patch 🙏🏻 

https://github.com/llvm/llvm-project/pull/216777