Edit env variables in u-boot source code before build

Hi,
I am building a custom image for am Apalis iMX6 V2.6 board and am following
http://developer.toradex.com/knowledge-base/build-u-boot-and-linux-kernel-from-source-code

I want t to edit the environmental variables before building the u-boot image

I assume it happens in a step between

make apalis_imx6_config

and

make -j3 2>&1 | tee build.log

where in the source can I edit before building, for example

vidargs, setupdate, etc.

Thanks!

That would be here.