When building tag system, let user to add some other pre-define could be considered

`// #define MY_DEFINE --> this is done by my own makefile`
`#ifdef MY_DEFINE`
`#include "file 1"`
`#else`
`#include "file 2"`
`some other code here refer to file 1 and cannot show information correctly`

The gtags cannot recognize MY_DEFINE and will try to search the information in file2
Is there any configuration to support this?