Run non-filechecked commands in update_cc_test_checks.py

Some tests in clang require running non-filechecked commands to generate the actual filecheck input. For example, tests for openmp offloading require generating the host bc without any checking, before running the clang command to actually generate the filechecked IR of the target device. This patch enables `update_cc_test_checks.py` to run non-filechecked run lines in-place.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D97068