Disable -Wcomment when building with GCC.

GCC version of -Wcomment is not compatible with ascii art graph diagrams.

Reverts r207629.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208073 91177308-0d34-0410-b5e6-96231b3b80d8
[ARM64] Enable alignment control option in front-end for ARM64.

This is the modification in llvm part.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208074 91177308-0d34-0410-b5e6-96231b3b80d8