[PATCH] clang-cl: Implement the -arch flag

[Ehsan Akhgari]

>>! In D4519#4, @hans wrote:
> If this is for PR20213 (though I guess this doesn't solve the SSSE3 problem?), please put that in the description.

Yes, it doesn't solve the SSE3 issue...

http://reviews.llvm.org/D4519