[compiler-rt] [sanitizer_common] Fix UnwindFast on SPARC (PR #101634)

[Tobias Hieta via llvm-commits]

tru wrote:

> @ebotcazou would be the natural reviewer, but for some reason I cannot select him.

That's because he's not part of the GitHub organization.

https://github.com/llvm/llvm-project/pull/101634