[yocto] Making machine config a build dependency for core-image recipes

[Yang, Fei]

I encountered a build issue when trying to generate /etc/inittab.
I have a meta-xxx/conf/machine/conf file which contains serial console information such as SERIAL_CONSOLE = "115200 ttyXYZ" or "115200 ttyS0" by default.
When I update that conf file and make an incremental build, the /etc/inittab doesn't get updated, I finally have to remove all the binaries and force a complete re-build to generate correct /etc/inittab with updated serial console settings, which take more than an hour to finish.
How do I create a dependency so that when I update my machine/conf file, an incremental build would take care of the change and re-generate the files in root FS accordingly? If that is impossible for now, can I just delete one or a few task binaries to trigger a rebuild on /etc/inittab? This would greatly reduce my build time.


Thanks,
Fei