MS syntax in Clang tests

Folks,

We had a few buildbot failures already because of x86-specific syntax
in MS tests, which just assume all back-ends are built. This is not
true nor will be for the foreseeable future.

So please, if you're adding an x86-specific, use FileCheck constraints
like REQUIRES or XFAIL or XPASS or add it to a target specific
directory. Whatever you need to restrict it to a specific
architecture.

http://llvm.org/docs/TestingGuide.html#platform-specific-tests

cheers,
--renato

Hi Renato,

the best folks can do is run tests locally and watch the bots afterwards, so some stuff will likely fall through the cracks every now and then. It’s probably easiest if you just fix the test when that happens. (See e.g. all of chapuni’s excellent work for keeping bots green.)