Add --no-cache-dir when building static wheels.

[Lukasa]

Per @geradcoles suggestion in #2338 and certifi/python-certifi#26.

[codecov-io]

Current coverage is 99.98%

Merging #2422 into master will not affect coverage as of 98e7d31

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[alex]

cc: @dstufft

[reaperhulk]

Should it be this flag or --no-use-wheel?

[Lukasa]

That's a good question: @dstufft would know.

[dstufft]

Probably you want --no-binary cryptography, like:

$ CFLAGS="-I${CWD}/openssl/include" LDFLAGS="-L${CWD}/openssl/lib" pip wheel --no-binary cryptogrpahy cryptography

I think that will do what you want... although it only works in the latest pip, the --no-use-wheel version is deprecated but does the same thing (though it applies to everything and not just cryptography).

[dstufft]

Specifically, the --no-use-wheel version is more compat with older versions, but is deprecated in favor of --no-binary.

[Lukasa]

@dstufft Is there any good reason not to use --no-use-wheel, then? I'm worried about providing instructions that only work with bleeding-edge pip.

[dstufft]

It'll go away at some point, but that's it.

[Lukasa]

Ok, I've switched to --no-use-wheel instead.

[coveralls]

Changes Unknown when pulling 09d1b47 on Lukasa:static-build-docs into ** on pyca:master**.