allow to build apps with other configs #1712

Job	Run time
read_targets_from_file / read_targets_from_file	4s
basic_build (cf2)	3m 46s
basic_build (bolt)	3m 39s
basic_build (tag)	3m 42s
basic_build (flapper)	3m 35s
apps (examples/app_hello_world)	2m 34s
kbuild-targets (allyesconfig)	3m 31s
apps (examples/app_hello_world-cpp)	2m 41s
features (bosch.conf)	3m 39s
kbuild-targets (allnoconfig)	3m 23s
features (loco_tdma.conf)	3m 34s
kbuild-targets (randconfig)	3m 24s
features (loco_tdoa2.conf)	3m 41s
apps (examples/app_hello_file_tree)	2m 39s
features (loco_tdoa3.conf)	3m 37s
apps (examples/app_peer_to_peer)	2m 41s
features (loco_tdoa3_all.conf)	3m 40s
apps (examples/app_p2p_DTR)	2m 35s
features (bigquad.conf)	3m 45s
apps (examples/app_stm_gap8_cpx)	2m 37s
features (app_api.conf)	3m 40s
apps (examples/demos/app_push_demo)	2m 39s
apps (examples/demos/swarm_demo)	2m 35s
apps (examples/demos/app_wall_following_demo)	2m 45s
	1h 14m 26s

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