clang: forward -no-integrated-as from the driver

Forward the -no-integrated-as option to -cc1 rather than simply invoking the
appropriate tool.  This is useful since this option has been overloaded to
permit disabling of parsing inline assembly at the MC layer.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@201952 91177308-0d34-0410-b5e6-96231b3b80d8