Other common targets are windows-gnu (MinGW) and windows-itanium, and occasionally windows-elf is used as well.
Updated, with a slightly different form of the regex, that also allows the triple to just end at -windows.
Alternatively, we could just remove this part of the lit config altogether. There's no other OSes that have target-<os> as a feature (only system-<os> for the host where the test is running), and after D68133 and D68136, no tests actually use this feature any longer.
In most cases, target restrictions rely on using a component of the triple. If all Windows-target triples are guaranteed to spell the component 'windows' then REQUIRES: windows works, and we don't need target-windows at all. But I was under the impression that win32 was used in the triple sometimes?
I'm going to assume that target-windows was added to deal with the common case of wanting to XFAIL a test for mingw and windows at the same time. Now that it's easy to match them as just XFAIL: windows or REQUIRES: windows, I don't think we really need this target-windows feature.
As you mention, there are two remaining tests using target-windows. If you want to update this patch to delete the target-windows feature and migrate them to just "windows", that works for me. Less code is always better.