Update the comment to mention that we use TTI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181178 91177308-0d34-0410-b5e6-96231b3b80d8
XFAIL for cygwin.

Looks like symbol resolution is not working on cygwin, the test fails
because __gxx_personality_v0 is not found.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181179 91177308-0d34-0410-b5e6-96231b3b80d8