Merged requested to merge wip/smcv/pathbuf-windows into main
The canonical directory separator is a backslash, but some Windows APIs allow either, interchangeably. Do the same here.
Resolves: #2914 (closed)
I haven't tested this, I'm entirely relying on the CI. If someone who runs Windows wants to take this over, please do!
/cc @ebassi @pwithnall @lrn