Is there a way to tell make to always accept the default flags?

The default behaviour after issuing "make install clean" is a "sysinstall" style blue window where the user can check and uncheck flags.

One way is to write all the flag options and values in make.conf prior to installation. I guess I could write a script that extracts the default flags from each Makefile and adds them to make.conf. But is there another, simpler way?