Update build_wheels

[jmalkin]

Sets cmake environment variables to fix build problems for Apple Silicon (aka arm64) devices. Previously, the CI task knew the build for both Intel and ARM instruction sets, but cmake was detecting the platform (Intel) and always using that. As a result, the underlying C++ library was never actually cross-compiled for the target platform.

This should (finally) fix the python library for non-Intel Macs.

[jmalkin]

This should address #304 and even #260 -- I never got feedback on the older one, but I am now confident that my previous attempt did not actually fix the issue. I have successfully tested this fix with the Apple Silicon version, and also confirmed that the Intel version would not load on an M1 Mac.

[coveralls]

Pull Request Test Coverage Report for Build 3111897280

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.347%

---

Totals
Change from base Build 3048941379:	0.0%
Covered Lines:	2196
Relevant Lines:	2378

---

💛 - Coveralls