Add a SIL test case for a dead alloc_stack with debug variable.
Add a SIL test case for a dead alloc_stack with debug variable.

benlangmuir/swift,atrick/swift,roambotics/swift,atrick/swift,rudkx/swift,glessard/swift,ahoppen/swift,gregomni/swift,gregomni/swift,JGiola/swift,glessard/swift,ahoppen/swift,roambotics/swift,apple/swift,apple/swift,apple/swift,JGiola/swift,gregomni/swift,gregomni/swift,apple/swift,JGiola/swift,ahoppen/swift,benlangmuir/swift,JGiola/swift,atrick/swift,benlangmuir/swift,atrick/swift,benlangmuir/swift,glessard/swift,JGiola/swift,rudkx/swift,ahoppen/swift,glessard/swift,roambotics/swift,gregomni/swift,rudkx/swift,JGiola/swift,ahoppen/swift,benlangmuir/swift,glessard/swift,rudkx/swift,roambotics/swift,gregomni/swift,benlangmuir/swift,atrick/swift,glessard/swift,ahoppen/swift,rudkx/swift,apple/swift,apple/swift,rudkx/swift,atrick/swift,roambotics/swift,roambotics/swift