This helps ensure we have even better consistency between them than before.
I could've used more conditionals here to reduce the amount of change, but it didn't seem worthwhile when it's pretty harmless to have them more consistent with one another instead.
This matches Go upstream's change to the same, and allows GOPATH on 1.17+ to move to C:\go (although with the caveat that GOPATH may not actually be useful for much longer).
See https://golang.org/cl/283600 for where this was changed in the official Go installer.