Build x86_64 thin wheel by default with py3.10

[isuruf]

No description provided.

[isuruf]

Ready for review.

Most important change here is that _PYTHON_HOST_PLATFORM and ARCHFLAGS are set so that universal2 wheels are not tried by default. This change is needed because python3.10 doesn't have a x86_64 only release and has only a universal2 build.

[matthew-brett]

Just to check my understanding - we need a way to use the PLAT variable to force the building of thin wheels? Here the idea is that the user can specify PLAT=x86_64 and then get a thin x86_64 wheel? But, they can also specify arm64 to get an ARM64 thin wheel?

Can you think of a test?

[isuruf]

Just to check my understanding - we need a way to use the PLAT variable to force the building of thin wheels? Here the idea is that the user can specify PLAT=x86_64 and then get a thin x86_64 wheel? But, they can also specify arm64 to get an ARM64 thin wheel?

Issue is that with python3.9 x86_64 installer, it built thin wheels by default, but with python3.10 universal2 installer
it tries to build universal2 wheels by default which is not what we want.

Yes, they can set PLAT=arm64 to get a ARM64 thin wheel without this PR. This PR adds the ability to build a thin wheel with 3.10

I'll think of a test

[rgommers]

LGTM. Can this be merged @matthew-brett? It's needed for MacPython/numpy-wheels#140