[PATCH] [x32] Introduce -mx32 flag enforcing x32 mode for other triplets

[Simon Atanasyan]

LGTM with a small nit

================
Comment at: lib/Driver/Driver.cpp:1925
@@ +1924,3 @@
+      AT = Target.get64BitArchVariant().getArch();
+      Target.setEnvironment(llvm::Triple::GNUX32);
+    } else if (A->getOption().matches(options::OPT_m32))
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AFAIK the `-mx32` is applicable to X86/x86_64 targets only. Let's ignore it for other targets. As to me I would prefer to show an error if -m16 or -mx32 provided for any targets except X86/x86_64. But that is another story.

http://reviews.llvm.org/D4470