Fix llc to not reuse spill slots in functions that invoke setjmp()

Fix llc to not reuse spill slots in functions that invoke setjmp()

We need to ensure that StackSlotColoring.cpp does not reuse stack
spill slots in functions that call "returns_twice" functions such as
setjmp(), otherwise this can lead to miscompiled code, because a stack
slot would be clobbered when it's still live.

This was already handled correctly for functions that call setjmp()
(though this wasn't covered by a test), but not for functions that
invoke setjmp().

We fix this by changing callsFunctionThatReturnsTwice() to check for
invoke instructions.

This fixes PR18244.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199180 91177308-0d34-0410-b5e6-96231b3b80d8