Reinstate aapcs as the default arm abi.

llvm-svn: 224490
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 111a383..77e4e12 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -794,10 +794,11 @@
     case llvm::Triple::EABI:
       ABIName = "aapcs";
       break;
-    // This is also the case for netbsd.
-    case llvm::Triple::GNU:
     default:
-      ABIName = "apcs-gnu";
+      if (Triple.getOS() == llvm::Triple::NetBSD)
+        ABIName = "apcs-gnu";
+      else
+        ABIName = "aapcs";
       break;
     }
   }