pyoxidizer: use in-memory resources on non-Windows platforms
In-memory resources were disabled for macOS in 7bc1beed, and for all platforms
in c900d962. Unfortunately this made it so that we were no longer producing
standalone binaries on these platforms, and would have to ship the .py and .pyc
files alongside the pyoxidized binary.
These changes are no longer necessary after f6b04591, which disabled pep517 and
solved the issue we were encountering.
Differential Revision: https://phab.mercurial-scm.org/D11734