ENH: Made UTILITY_SOURCE command inherited, just like FIND_PROGRAM.

Source/cmUtilitySourceCommand.h

@@ -45,6 +45,12 @@ public:
    */
   virtual bool Invoke(std::vector<std::string>& args);
 
+  /**
+   * This determines if the command gets propagated down
+   * to makefiles located in subdirectories.
+   */
+  virtual bool IsInherited() { return true;  }
+
   /**
    * The name of the command as specified in CMakeList.txt.
    */