How to set to "ALT_LEGACY_INTERRUPT_API_PRESENT"

hello,

In Nios II Software Developer’s Handbook (January 2014) P8-11,

I found following information.

When the SBT selects the interrupt API, it defines one of the following symbols in

system.h, to identify which interrupt API is available:

■ ALT_ENHANCED_INTERRUPT_API_PRESENT

—Defined if the enhanced API is implemented

■ ALT_LEGACY_INTERRUPT_API_PRESENT

—Defined if the legacy API is implemented

Does it mean to edit system.h directory?

I confirmed that edited system.h works correctly.

But in this method, I need edit every time after generating BSP.

Is there more smart way such as setting GUI switch or other permanent FLAG.

Thank you.