Revert CPU detection code to return "generic" instead of an empty string in case
of failure. The x86 target didn't like empty cpu names and broke x86 tests on
non-x86 buildbots.

llvm-svn: 89111
diff --git a/llvm/lib/System/Host.cpp b/llvm/lib/System/Host.cpp
index 0faf8fe..37591a5 100644
--- a/llvm/lib/System/Host.cpp
+++ b/llvm/lib/System/Host.cpp
@@ -249,7 +249,7 @@
     }
 
     default:
-      return "";
+      return "generic";
     }
   } else if (memcmp(text.c, "AuthenticAMD", 12) == 0) {
     // FIXME: this poorly matches the generated SubtargetFeatureKV table.  There
@@ -289,10 +289,10 @@
       case 16:
         return "amdfam10";
     default:
-      return "";
+      return "generic";
     }
   }
 #endif
 
-  return "";
+  return "generic";
 }