X86: Mark non-crashing report_fatal_errors() as such.

Previously, the clang crash handling code would kick in and give a crash
report for these, even though they're not that sort of error.

rdar://14882264

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189878 91177308-0d34-0410-b5e6-96231b3b80d8