bpo-45020: Drop the frozen .h files from the repo.

[ericsnowcurrently]

This is essentially an un-revert of gh-28375 (reverted in gh-28380). I reverted it due to a (single) buildbot failure. I've adjusted the code we generate for frozen modules in the makefile, based on a hunch about the make version, to fix it.

(Note that I also remove the frozen __hello__.h file, which I missed in the original PR.)

https://bugs.python.org/issue45020

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @ericsnowcurrently for commit b9d87111a6698b4825e4cf7c4355ee0f45902abf 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[ericsnowcurrently]

I'm going to watch the buildbots and make sure the earlier problem is resolved here.

[gvanrossum]

FWIW, I kind of doubt that removing the $(srcdir)/ prefix from the files in FROZEN_FILES would fix that buildbot job, but we'll find out eventually if it matters to anyone. (My hunch is that it was a random failure; there are several other variables defining lists of .h files used as dependencies that also use $(srcdir)/.)