Make sure TableGen exits with an error code after printing errors.

This makes it possible to report multiple errors in one invocation.
There are already calls to PrintError in CodeGenDAGPatterns.cpp which
previously would not cause TableGen to fail.

<rdar://problem/13463339>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177573 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/TableGen/Main.cpp b/lib/TableGen/Main.cpp
index e1cd623..dc4167b 100644
--- a/lib/TableGen/Main.cpp
+++ b/lib/TableGen/Main.cpp
@@ -117,11 +117,14 @@
   if (MainFn(Out.os(), Records))
     return 1;
 
+  if (ErrorsPrinted > 0) {
+    errs() << argv0 << ": " << ErrorsPrinted << " errors.\n";
+    return 1;
+  }
+
   // Declare success.
   Out.keep();
   return 0;
-
-  return 1;
 }
 
 }