[BOLT] Enable lit internal shell by default
This patch enables lit's internal shell by default now that all
REQUIRES: shell tests have been update to not require shell features not
available in lit and all unresolved tests have been fixed.
This should speed up test runtime by a bit and will give nicer error
messaging.
Fixes #102701.
Reviewers:
aaupov, yota9, maksfb, paschalis-mpeis, yozhu, rafaelauler, ayermolo
Reviewed By: maksfb
Pull Request: https://github.com/llvm/llvm-project/pull/156083
