Reverts llvm/llvm-project#96802
Attempt #5 fails. It's been 6 months. I despise Makefile.rules and have
no ability to even *detect* these failures without _landing_ a diff. In
the mean time, we have no testing for DWP files at all (and a regression
that was introduced, that I fix with this diff) so I'm going to just
remove some of the tests and try to land it again, but with less testing
I guess.