[Clang][test] Avoid FileCheck error when matching `-cc1`

FileCheck patterns consisting of only `-cc1` on a line by itself often
cause mismatches, e.g. with version strings formed from commit hashes
such as "clang-cc1514432c58". They should be changed to contain more
context and match more precisely.

Differential Revision: https://reviews.llvm.org/D141886