Based on this wiki https://wiki.openwrt.org/doc/howto/obtain.firmware.generate We can build openwrt images like this:
make image PROFILE=XXX PACKAGES="pkg1 pkg2 pkg3 -pkg4 -pkg5 -pkg6" FILES=files/
Note that the list of PACKAGES must be in the openwrt repo.
But I have my own packages that aren't in the repository, they're ipk files that I compiled on my own. How do I get these packages installed during the build ?