gh-560: Add Windows PGO NoGIL builder

[itamaro]

No description provided.

[itamaro]

@zware @mdboom if there are no concerns with the implementation, I will merge this tomorrow, when I can keep an eye on the Windows worker more closely.

[db3l]

@itamaro, if you could, when you enable this tomorrow, could you specifically take a peek at how test_cext does?

It looks like it's been failing on my new PGO builder. I haven't had a lot of time to look into it, but from what I can tell it didn't run in the past as it skips debug mode on Windows - but the PGO builder is no longer debug mode. I didn't notice this during my manual test as I hadn't enabled the "cpu" resource so it didn't even try test_cext.

What I'm not sure is whether test_cext should be modified to skip any Windows build, or just PGO, or if it ought to work in release/pgo mode and the PGO builder is just highlighting something on my worker.

[vstinner]

LGTM

[mdboom]

LGTM

[itamaro]

@db3l test_cext passed, but 5 other tests failed (test_call test_class test_functools test_int test_ssl)

logs: https://buildbot.python.org/#/builders/1622/builds/1/steps/5/logs/stdio