Add option to disable module loading.

This patch was created by Lawrence Crowl and reviewed in:
http://llvm-reviews.chandlerc.com/D963

llvm-svn: 187738

clang/lib/Frontend/CompilerInvocation.cpp

@@ -872,6 +872,8 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
   Opts.ResourceDir = Args.getLastArgValue(OPT_resource_dir);
   Opts.ModuleCachePath = Args.getLastArgValue(OPT_fmodules_cache_path);
   Opts.DisableModuleHash = Args.hasArg(OPT_fdisable_module_hash);
+  // -fmodules implies -fmodule-maps
+  Opts.ModuleMaps = Args.hasArg(OPT_fmodule_maps) || Args.hasArg(OPT_fmodules);
   Opts.ModuleCachePruneInterval =
       getLastArgIntValue(Args, OPT_fmodules_prune_interval, 7 * 24 * 60 * 60);
   Opts.ModuleCachePruneAfter =