modify Cmake path to be independent of compile dir

[carlnotsagan]

typo in relative path for Cmake file variant patch

[Yurlungur]

This is not a typo---it depends on where you call cmake. However what's in there currently is a hack---there's a more robust way to do this, which I will try to thread through.

[carlnotsagan]

ok, makes sense, ive changed the title of the pr to reflect that