[Modules] If a module map resides in a system header directory, treat it as a system module.

This prevents -pedantic from causing warnings in the system headers
used to create modules. Fixes <rdar://problem/14201171>.

llvm-svn: 184560
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index a2872dd..8011a8b 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -881,7 +881,7 @@
 
 
   // Construct a module-generating action.
-  GenerateModuleAction CreateModuleAction;
+  GenerateModuleAction CreateModuleAction(Module->IsSystem);
   
   // Execute the action to actually build the module in-place. Use a separate
   // thread so that we get a stack large enough.