[compiler-rt] [builtins] Fix floattitf.c etc. compilation on Solaris/SPARC (PR #70058)

[Alex Bradbury via llvm-commits]

https://github.com/asb approved this pull request.

This LGTM, thanks for fixing this and apologies my patch caused a regression for your target. Failing to guard int128_t was indeed an oversight.

Looking at the history for the linked builder, it seems pretty reliable other than this patch of course breaking it. Have you looked into [moving it to the production buildmaster](https://llvm.org/docs/HowToAddABuilder.html#steps-to-add-builder-to-llvm-buildbot)? That way, I would have had an email soon after landing the patch and could have reverted then fixed.

https://github.com/llvm/llvm-project/pull/70058