Change jaxlib build rules to build a wheel package.

[hawkinsp]

Before this PR, the jaxlib build script (build/build.py) writes its output to build/ subdirectory of the jax source tree. This is a bit ugly since it intermingles the jax source tree with the artifacts built from it (an unpacked wheel).

This PR changes the build scripts to build a .whl package as the output of running build.py, which is by default written to the dist/ subdirectory of the current directory.

Also remove mentions of cython as a build dependency. We don't need the user to provide cython, bazel downloads it. six also seems unused.

[hawkinsp]

@cloudhan

[cloudhan]

Hmm, it take me time to figure out why from wheel import pep425tags fails, turns out it has been removed in 0.35 of wheel
See pypa/wheel#370 and pypa/wheel@a519770

[hawkinsp]

Hmm, it take me time to figure out why from wheel import pep425tags fails, turns out it has been removed in 0.35 of wheel
See pypa/wheel#370 and pypa/wheel@a519770

I just noticed that too. I already pushed a new version that fixes this.

[cloudhan]

tmpdir.cleanup() is causing the same problem.

[hawkinsp]

tmpdir.cleanup() is causing the same problem.

Can you verify you are using commit c06ead6 ?

In particular I was seeing that until I added an extra os.chdir to make sure the current directory wasn't inside the temp dir when it was deleted.

[cloudhan]

I think I'll wait you merge this PR and fix that later.

[cloudhan]

I am on that commit. But cleanup is calling into rmtree and rmtree will refuse to delete readonly pyd file. 😂