win32 should have a _distributor_init.py and preload DLLs

[mattip]

fixes numpy/numpy#13764

In numpy/numpy#13109 we preload any dlls as a way around other methods of solving dll hell. That code should live here, as part of a _distributor_init.py file. In addition, the win32 CI run should run a sanity check on the wheel it builds in a clean environment.

The transferred code should also add a try except for the case where __file__ does not exist.

[mattip]

PR #50 was meant to fix this, but looking at the [artifact], the _distributor_init.py was not overwritten.

[mattip]

The _distributor_init.py is now overwritten but the contents are not correct

[charris]

What should it be? I can see the contents by downloading the wheel created after merge from https://7933911d6844c6c53a7d-47bd50c35cd79bd838daf386af554a83.ssl.cf2.rackcdn.com/

[mattip]

See PR #52 - I found the base directory improperly

[charris]

I see libopenblas.FN5FF57TWHUYLRG54LA6B33EZPHYZZL4.gfortran-win32.dll, which is not correct. I wonder where that came from.

[mattip]

I am pretty sure that is the dll we have been shipping, the problem was I was looking for .libs one directory higher

[charris]

We should be shipping libopenblas_v0.3.5-gcc_7_1_0.dll, does it get renamed somewhere?

[charris]

OK, that looks correct, agrees with 1.16.4. So it does get renamed along the line somewhere.