No longer emitting a PCH file when using -fsyntax-only on a header file.  Fixes PR13343.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161019 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 5be60b8..671c0ac 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -1210,8 +1210,14 @@
     }
     return new PreprocessJobAction(Input, OutputTy);
   }
-  case phases::Precompile:
-    return new PrecompileJobAction(Input, types::TY_PCH);
+  case phases::Precompile: {
+    types::ID OutputTy = types::TY_PCH;
+    if (Args.hasArg(options::OPT_fsyntax_only)) {
+      // Syntax checks should not emit a PCH file
+      OutputTy = types::TY_Nothing;
+    }
+    return new PrecompileJobAction(Input, OutputTy);
+  }
   case phases::Compile: {
     if (Args.hasArg(options::OPT_fsyntax_only)) {
       return new CompileJobAction(Input, types::TY_Nothing);