Prevent test_tools from copying 1000M of "source"
It doesn't need a git repo, just the checkout. We skip .git metadata, Doc/build, Doc/venv, and `__pycache__` subdirs, that developers often have in their clients to reduce the size of the source tree copy ten-fold.
This should significantly reduce IO and presumably time on buildbots during this long test.
This gains 10% or more in startup time for `python -c pass` on UNIX-ish systems.
The Makefile.pre.in generating code builds on Eric's work for bpo-45020, but the .c file generator is new.
Windows version TBD.
The "freeze" tool has been part of the repo for a long time. However, it hasn't had any tests in the test suite to guard against regressions. We add such a test here. This is especially important as there has been a lot of change recently related to frozen modules, with more to come.
Note that as part of the test we build Python out-of-tree and install it in a temp dir.
https://bugs.python.org/issue45629
Erlend E. Aasland
Gregory P. Smith
Victor Stinner
Inada Naoki
Eric Snow
Guido van Rossum
Serhiy Storchaka
Martin v. Löwis