Xcode: Disable implicit make rules in custom rules makefiles.

With apologies to the suggester for not accenting the surname
vowel properly.

Suggested-By: Johan Bjork

Source/cmGlobalXCodeGenerator.cxx

@@ -1279,6 +1279,9 @@ void  cmGlobalXCodeGenerator
   makefileStream << "# Generated by CMake, DO NOT EDIT\n";
   makefileStream << "# Custom rules for " << target.GetName() << "\n";
 
+  // disable the implicit rules
+  makefileStream << ".SUFFIXES: " << "\n";
+
   // have all depend on all outputs
   makefileStream << "all: ";
   std::map<const cmCustomCommand*, cmStdString> tname;