How to force build of package if other targets image changed?

[kestrel]

Hi,

I am currently looking into fritzbox 7490, which has two SoC. One is lantiq xrx200 and the other is ath79 (where the two wifis are connected and it has no flash or persistent storage so it always has to be ram-booted).
I tried to create a package for the lantiq image, which copies the ath79 image into the file system of the lantiq image to be able to run scripts on the lantiq to boot the ath79 image.
But the problem is, if I recreate the ath79 image, my lantiq package does not get driven by make, because the file is already in the lantiq-root of the build directory.
I have looked into other samples makefiles and added the ath79-generic-initramfs.bin to PKG_CONFIG_DEPENDS or PKG_DEPENDS, but that has not helped. Is there a PKG_FLAG or something which can force the build of my package copying the ath79 initramfs bin into the lantiq-root directory every time the lantiq image is build or at least if it was changed?
I tried prebuild hooks etc. but it seems that as long as the initramfs is present in the lantiq-root build directory, the makefile does not even get triggered.
At one point in time the ath79 initramfs bin got copied into the staging_dir but not into build dir, any ideas?

Thanks in advance.

[vgaetera]

Perhaps this can help:

Using Build Environments

[slh]

I don't think depending on build artifacts of different targets will be possible in an automated fashion, not without rather huge refactoring of the buildsystem. It's probably easier if you treat the generated ath79 initramfs image as a binary firmware and bump the package definition manually, as needed.

[kestrel]

Ok, thanks, for my own builds I just add another copy to the makefile.