ENH: remove dangerous access to ivar that should not be used

Source/cmake.h

@@ -314,7 +314,6 @@ class cmake
    */
   const char* GetCTestCommand();
   const char* GetCPackCommand();
-  const char* GetCMakeCommand() const { return this->CMakeCommand.c_str(); }
 
   // Do we want debug output during the cmake run.
   bool GetDebugOutput() { return this->DebugOutput; }