[compiler-rt] Reapply "[compiler-rt] Default to Lit's Internal Shell" (PR #168232)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

It looks like the ppc64le failures were never real in the first place. The bot seems to fail ~50% of its runs on some compiler-rt test or another.

https://github.com/llvm/llvm-project/pull/168232