Install custom builds of p4python on arm64.
Review Request #11949 — Created Jan. 20, 2022 and submitted
As of right now, there are no official arm64 builds of p4python
available from Perforce, and this has impacted our testing.
We've built our own arm64 builds and made them public. This change
allows pip to consider those for installation when on this platform.
Tested installing on my Apple M1 on all supported versions of Python.
Unit tests pass.