Map GCC's flag_stack_protect == 3 to LLVM's StackProtectStrong.


git-svn-id: https://llvm.org/svn/llvm-project/dragonegg/trunk@191023 91177308-0d34-0410-b5e6-96231b3b80d8
Some linux distributions have patched their system gcc to turn on the
stack protector by default.  Ensure this test passes on such systems.


git-svn-id: https://llvm.org/svn/llvm-project/dragonegg/trunk@191024 91177308-0d34-0410-b5e6-96231b3b80d8