[Clang] Invoke shell script with bash
This test attempts to run a reproducer script generated by clang. This
is intended to be run by a shell, so invoke it with an actual shell.
This enables running the test with LLVM lit's internal shell.
Reviewers: bcardosolopes, ilovepi, petrhosek
Reviewed By: ilovepi
Pull Request: https://github.com/llvm/llvm-project/pull/157608
