Fix refacto, gcc's cc1 needs to see --output-pch=, which is not just an alias
for -output-pch=.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89534 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 265987e..69de2d3 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1704,7 +1704,7 @@
     // to be a good reason.
     CmdArgs.push_back("/dev/null");
 
-    CmdArgs.push_back("-output-pch=");
+    CmdArgs.push_back("--output-pch=");
     CmdArgs.push_back(Output.getFilename());
   }