[llvm] [llvm][tblgen] Add `SourcePath` for `emitSourceFileHeader` (PR #65744)

[Tobias Hieta via llvm-commits]

tru wrote:

Looking at it - it seems like none of Tablegen is correctly clang-formatted. If that's not desired, maybe it should have a local .clang-format file to disable the formatting of these files.

Do we have a clang-tblgen maintainer? Couldn't find anything in the codeowners and git log history seems to be very split.

https://github.com/llvm/llvm-project/pull/65744