Added comments for wchar_size drop

Author: aidan.belton

libclc/utils/prepare-builtins.cpp

@@ -75,7 +75,8 @@ int main(int argc, char **argv) {
   if (NamedMDNode *OCLVersion = M->getNamedMetadata("opencl.ocl.version"))
       M->eraseNamedMetadata(OCLVersion);
 
-  // Drop wchar_size module flag
+  //wchar_size flag can cause a mismatch between libclc libraries and 
+  //modules using them. Since wchar is not used by libclc we drop the flag
   if (M->getModuleFlag("wchar_size")) {
     SmallVector<Module::ModuleFlagEntry, 4> ModuleFlags;
     M->getModuleFlagsMetadata(ModuleFlags);