[Driver][ARM64] Make sure the default CPU is passed to the assembler.

<rdar://problem/16573920>

llvm-svn: 206227
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 9eb6fd4..5bc7d5e 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -1336,6 +1336,9 @@
   case llvm::Triple::aarch64_be:
     return getAArch64TargetCPU(Args, T);
 
+  case llvm::Triple::arm64:
+    return getARM64TargetCPU(Args);
+
   case llvm::Triple::arm:
   case llvm::Triple::armeb:
   case llvm::Triple::thumb: