ARM64: override all the things.

Actually, mostly only those in the top-level directory that already
had a "virtual" attached. But it's the thought that counts and it's
been a long day.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205131 91177308-0d34-0410-b5e6-96231b3b80d8
ARM64: remove -m32/-m64 mapping with ARM.

This is causing the ARM build-bots to fail since they only include
the ARM backend and can't create an ARM64 target.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205132 91177308-0d34-0410-b5e6-96231b3b80d8