AAPT2: Fix windows multiple directory creation

When attempting to create directories on different drives, AAPT2 would
fail because it would attempt to call _wmkdir on the drive
(eg. _wmkdir("D:\")). Split on directories after the drive letter
instead.

Bug: 68936311
Test: manual testing using Android Studio
Change-Id: Iad47f466af6f82d4ac402e9bf52853edaa9a5e0b