Propagate "-arch x86_64h" setting to the linker. <rdar://problem/15711488>

This is a follow-up to r194907, which added a new -arch setting to make it
easier to specify AVX2 targets. The "-arch x86_64h" option needs to be passed
on to the linker, but it was getting canonicalized to x86_64 by the code
in getArchTypeForDarwinArchName.

llvm-svn: 198096
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 5ccd041..3174def 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -1868,17 +1868,24 @@
   if (Target.isOSDarwin()) {
     // If an explict Darwin arch name is given, that trumps all.
     if (!DarwinArchName.empty()) {
-      Target.setArch(
-        tools::darwin::getArchTypeForDarwinArchName(DarwinArchName));
+      if (DarwinArchName == "x86_64h")
+        Target.setArchName(DarwinArchName);
+      else
+        Target.setArch(
+          tools::darwin::getArchTypeForDarwinArchName(DarwinArchName));
       return Target;
     }
 
     // Handle the Darwin '-arch' flag.
     if (Arg *A = Args.getLastArg(options::OPT_arch)) {
-      llvm::Triple::ArchType DarwinArch
-        = tools::darwin::getArchTypeForDarwinArchName(A->getValue());
-      if (DarwinArch != llvm::Triple::UnknownArch)
-        Target.setArch(DarwinArch);
+      if (StringRef(A->getValue()) == "x86_64h")
+        Target.setArchName(DarwinArchName);
+      else {
+        llvm::Triple::ArchType DarwinArch
+          = tools::darwin::getArchTypeForDarwinArchName(A->getValue());
+        if (DarwinArch != llvm::Triple::UnknownArch)
+          Target.setArch(DarwinArch);
+      }
     }
   }