[compiler-rt] [nfc][lsan] Restructure loop in ProcessThreads (PR #112609)

[Vitaly Buka via llvm-commits]

vitalybuka wrote:

> LLVM Buildbot has detected a new failure on builder `clang-hip-vega20` running on `hip-vega20-0` while building `compiler-rt` at step 3 "annotate".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/123/builds/7655
> 
> Here is the relevant piece of the build log for the reference

flake

https://github.com/llvm/llvm-project/pull/112609