[clang-tidy] Don't error on MS-style inline assembly.

To get MS-style inline assembly, we need to link in the various
backends.  Some other clang tools already do this, and this issue
has been raised with clang-tidy several times, indicating there
is sufficient desire to make this work.

Differential Revision: https://reviews.llvm.org/D38549

llvm-svn: 316246