tests: fix PYTHONPATH manipulation on Windows
Without the semicolon separator and quotes, the variables ends up like this:
c:\Users\Matt\projects\hg-evolve:c:\Users\Matt\projects\hg-evolve:
c:\Users\Matt\projects\hg;c:\Users\Matt\projects\hg-evolve\tests;
c:\Users\Matt\projects\hg\tests
That in turn makes the local evolve code unreachable, and the system installed
code is tested instead.
I'm testing against `uname` instead of a trivial python script printing os.name
because maybe one day tests will run on WSL.
test-drop.t
test-inhibit.t
test-simple4server.t
tests/test-simple4server-bundle2.t