Add a test case for generic specialization with borrow scope fixup.
Add a test case for generic specialization with borrow scope fixup.

This tests a borrow scope whose use becomes unreachable. The liveness
utilities need to work on this malformed SIL in order to fixup OSSA
on-the-fly.

roambotics/swift,roambotics/swift,roambotics/swift,apple/swift,apple/swift,apple/swift,apple/swift,roambotics/swift,apple/swift,roambotics/swift,roambotics/swift,apple/swift