Fixes: #27934
This commit introduces additional naming support of config files.
It is now possible to create a config file of the form
`prj_<build>.conf` and automatically have a corresponding
`boards/<BOARD>_<build>.conf` config file merged.
As example, one can create a structure as:
|-- prj.conf
|-- prj_debug.conf
|-- boards
|-- nrf52840dk_nrf52840.conf
|-- nrf52840dk_nrf52840_debug.conf
when building: (existing behavior)
cmake -DBOARD=nrf52840dk_nrf52840 ...
prj.conf is merged with nrf52840dk_nrf52840.conf
when building: (new behavior)
cmake -DBOARD=nrf52840dk_nrf52840 -DCONF_FILE=prj_debug.conf ...
prj_debug.conf is merged with nrf52840dk_nrf52840_debug.conf
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>