bug#53340: t/instmany-python.sh failure w/automake-1.16.2 under Gentoo

[Mike Frysinger]

turns out this doesn't repro in official automake versions because it requires a
Gentoo-specific patch -- the one sent for #38043 to fix Python 3.5+ compilation.
the issue is that lib/am/python.am chops up the list of files before the globs
are expanded instead of after.

## This is somewhat tricky, because for newer pythons we have to take PEP-3147
## into account.  Avoid exceeding the command-line length limit.
    dir='$(DESTDIR)$(%NDIR%dir)'; \
>   echo "$$py_files" | $(am__pep3147_tweak) | $(am__base_list) | \
      while read files; do \
        $(am__uninstall_files_from_dir) || st=$$?; \
      done || exit $$?; \
    exit $$st

the > line above will turn the list of files we installed into a bunch of globs
(e.g. py_files="npython1.py" turns into "__pycache__/npython1.*.pyc
__pycache__/npython1.*.pyo"), and then those globs (before they're expanded) run
through $(am__base_list) to chop them up into sets of 40, but then we have 40
globs that expand into a lot more files.  before #38043, we have 1-to-2 
increase,
but now we have 1-to-3, and so the command line is exceeded.

so we have to expand the globs between $(am__pep3147_tweak) and 
$(am__base_list).
-mike