Useful to only create a new image with only small diff with for example
aarch64_defconfig.
example:
If the only diff is the VENDOR, instead of KernelKit you want 'foobar'.
create a file with the change:
INFIX_VENDOR="foobar"
and call ./utils/generate-defconfig.sh -b aarch64_defconfig -c foobar-diff.conf -o configs/foobar_defconfig
