Disable the Thumb no-return call optimization:

Disable the Thumb no-return call optimization:
mov lr, pc
b.w _foo

The "mov" instruction doesn't set bit zero to one, it's putting incorrect
value in lr. It messes up backtraces.

rdar://12663632

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167657 91177308-0d34-0410-b5e6-96231b3b80d8