[coreboot] question about CFLAGS custom

[Yoshinoya]

Hi,
I am studying coreboot source code.
I have a question about how to costom CFLGAS.

There is a Makefile.inc in the root of source code.
I found some CFLAGS_common definition.
Could i change CFLAGS setting in this file?
And this changes could take effects in the whole coreboot module compile time?

Thanks