[FEATURE] expose Linux overlay build option in FW versioning/logs somehow

[kv2019i]

Is your feature request related to a problem? Please describe.
Filing based on discusison in:
#10356

""We do need to figure out some way to identify the overlay use in FW version. Upto now, the combination of SOF version and hw target, has been unique so any bug reports could have been tracked to a specific source/build configuration. With the overlay, this link is broken and we can't anymore figure out from kernel/FW logs, how the FW was built. I'll probably file a ticket for this.""

[lgirdwood]

@kv2019i does it make sense to have something like a Kconfig OVERLAY_NAME string that set by the overlay or empty ? This could be published by logs or in boot message ?