When we removed the com suffix from ape binaries, we broke the build for
ape's python for any case-insensitive file system, i.e. Windows and XNU,
because there is a third_party/python/Python that gets mirrored in the o
directory with the python object files and clashes with the binary name.
This patch hacks around this by renaming the binary to "python3" so that
it no longer clashes with that directory.
