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