Switch Wmodule-build to a remark

On reflection, this is better despite the missing command-line handling
bits for remarks.  Making this a remark makes it much clearer that
this is purely informational and avoids the negative connotations of a
'warning'.

llvm-svn: 208367
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index da0ca46..9e07e74 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1212,7 +1212,7 @@
         return ModuleLoadResult();
       }
 
-      getDiagnostics().Report(ImportLoc, diag::warn_module_build)
+      getDiagnostics().Report(ImportLoc, diag::remark_module_build)
           << ModuleName << ModuleFileName;
 
       // Check whether we have already attempted to build this module (but