[llvm-branch-commits] [UpdateTestChecks] Cleanly support .ifdef and .macros in update_mc_test_checks.py (PR #199305)

[Alexander Richardson via llvm-branch-commits]

arichardson wrote:

<!-- spr-dependencies -->
This is a stacked pull request managed by [spr](https://github.com/spacedentist/spr). The following pull requests must be merged before this one:

<!-- spr-dependencies-list-start -->
- #198936
- #199298
<!-- spr-dependencies-list-end -->


https://github.com/llvm/llvm-project/pull/199305