[clang] [Clang] Add __builtin_bswapg (PR #162433)

[via cfe-commits]

clingfei wrote:

The reason for the failure is that the target platform does not support __int128. If the target platform does not support __int128, perhaps we should skip testing it.

> > LLVM Buildbot has detected a new failure on builder `clang-armv8-quick` running on `linaro-clang-armv8-quick` while building `clang` at step 5 "ninja check 1".
> > Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/24121
> > Here is the relevant piece of the build log for the reference
> 
> This test failure has been there for over 12 hours at this point. @clingfei and @ojhunt, could one of you either fix the test or revert if you need to investigate?

I am not sure what you mean by "fix the test", could you please provide a guide?

https://github.com/llvm/llvm-project/pull/162433