Add option to include overlay bundles as part of the initramfs structure

[ivandavidov]

One use case is the DHCP client funstionality.

If we have the DHCP client functionality as overlay bundle, there is high chance that it won't work properly on real hardware because the kernel provides minimal configuration and as result many devices may not be recognized, including the boot device. In this case all overlay bundles won't be accessible.

So, if we want to ensure that certain functionality is really there, it should be part of the initramfs structure.

This would require some major reachitecturing because the overlay bundles should be available before the initramfs structure has been packaged. Another challenge is to redesign the overlay bundles so that they generate independent structure which then could be merged with the initramfs structure.

[ivandavidov]

This feature has been implemented here. There is new config options which specifies the 'merge' location.

[ivandavidov]

The functionality has been tested and it works fine. However, from usability point of view it is recommended to use this only if you want to use MLL on real hardware. Otherwise the default build behavior is more than sufficient for VMs and it has been proven to work.