[clang] [llvm] [GitHub][CI] Add running of 'dump_ast_matchers.py' to premerge workflow (PR #165472)

[Aiden Grossman via cfe-commits]

https://github.com/boomanaiden154 commented:

Why do we need to do something in the code formatting action that's completely custom instead of something like https://github.com/llvm/llvm-project/pull/118154?

Also, this should probably just be autogenerated inside the build system.

I tried this for the example above in https://github.com/llvm/llvm-project/pull/113739, but maintainers were not happy.

https://github.com/llvm/llvm-project/pull/165472