correct virtualenv bin dir under mingw python

[davidhewitt]

I believe this fixes #630

... at least, I was able to remove the workaround I had in PyO3/setuptools-rust#501

Open to alternative ideas / suggestions how you'd like this tested.

[henryiii]

The idiomatic thing is to use sys.platform.startswith, which also happens to be correct here, I think: https://stackoverflow.com/questions/446209/possible-values-from-sys-platform

[henryiii]

We might need to be careful mocking (see #902), but I'm curious to see if this runs first.

[henryiii]

Could you make sure this also fixes your issue? I think it's a better fix and should handle Cygwin and such too.

[davidhewitt]

Sorry for the delay, I finally reran on the setuptools-rust CI and it looks like this branch didn't work, I'll try to debug when I get the chance.

[davidhewitt]

Ok so I had a debugging session and it seems like sys.platform is still just win32, so that seems to be insufficient to detect msys2. The MSYS2 portability docs seem to explicitly point to using sysconfig.get_platform() in https://www.msys2.org/docs/python/

I restored the _IS_MINGW check against sysconfig.get_platform(), and it's fixed the workflow again. Would you like me to push a (mocked) test?

[davidhewitt]

I found a brief moment to push a test, hopefully looks suitable. Happy New Year!