pmbootstrap can't parse dynamically generated list of subpackages

When installing device-pine-a64lts, installation will fail on not being able to find the package u-boot-pine64. This is a subpackage of u-boot, but doesn't exist in the binary repos yet. First building u-boot and then installing the device package works however.

I guess pmbootstrap has to parse all subpackages somehow, and build the parent package if the subpackage exists as an aport but not as a compiled package.