Currently, pyoxidizer.bzl does not mention the git commit that should be checked
out, so these instructions are a bit difficult to follow right now (impossible,
technically), so I removed the instruction to git checkout <Git commit> and
the admonition to use a specific version of PyOxidizer. I don't even know if the
project currently builds with the "0.7.0-pre" version that was previously
As fallout from that change to not "pin" to a specific PyOxidizer, I had to
update the Python version to use when running the tests.
While here, I added a recommendation to use --release, as the primary reason
for this project is performance, and it may have been leaving some on the table
to not have that there.