force / in actual_path() on Windows

[altendky]

This is intended to make relative paths generated on Windows usable in Linux and macOS.

https://github.com/nedbat/coveragepy/issues/991

Draft for:

• [ ] Tests
• [ ] Discussion around better solutions or other places that should be addressed.

[altendky]

So this trivial change ran ok in my single test usage at https://github.com/Chia-Network/chia-blockchain/runs/6972851503?check_suite_focus=true, but a bunch of tests fail here. I'll keep looking around and trying to get a better feel but if you have some design guidance in mind, what with you actually knowing the code base already :], I'm all ears. Or eyes, I suppose.

[nedbat]

I think this has been handled in commit 7df8609f.