SB_CONF_FILE
Sysbuild Kconfig configuration file, or list of files.
Defaults to sysbuild.conf in APPLICATION_CONFIG_DIR, if that file
exists. Sysbuild is an opt-in feature, so the file is optional.
Settings in these files override the defaults of sysbuild’s own Kconfig tree. Paths are resolved
relative to APP_DIR.
See sysbuild_kconfig.