[UpdateCCTestChecks] Support --check-globals

This option is already supported by update_test_checks.py, but it can
also be useful in update_cc_test_checks.py.  For example, I'd like to
use it in OpenMP offload codegen tests to check global variables like
`.offload_maptypes*`.

Reviewed By: jdoerfert, arichardson, ggeorgakoudis

Differential Revision: https://reviews.llvm.org/D104714