Re-land "[Clang][Driver] Remove -M group options ..." and "[Clang] Avoid...

Re-land "[Clang][Driver] Remove -M group options ..." and "[Clang] Avoid crashing when generating crash diagnostics when '#pragma clang __debug ..."

This re-lands commits f41ec709 (https://reviews.llvm.org/D74076)
and commit 5fedc2b4 (https://reviews.llvm.org/D74070)

The previous build break was caused by '#pragma clang __debug llvm_unreachable' used in a non-assert build. Move it to a separate test in crash-report-with-asserts.c.