fixed the way of building apps with any disired config #1735

Job	Run time
read_targets_from_file / read_targets_from_file	4s
basic_build (cf2)	3m 40s
basic_build (bolt)	3m 39s
basic_build (tag)	3m 43s
basic_build (flapper)	3m 38s
kbuild-targets (allyesconfig)	5m 44s
features (bosch.conf)	3m 36s
apps (examples/app_hello_world)	7m 21s
kbuild-targets (allnoconfig)	4m 4s
apps (examples/app_hello_world-cpp)	2m 40s
kbuild-targets (randconfig)	5m 14s
features (loco_tdma.conf)	4m 20s
apps (examples/app_hello_file_tree)	3m 45s
features (loco_tdoa2.conf)	6m 17s
apps (examples/app_peer_to_peer)	4m 21s
features (loco_tdoa3.conf)	6m 41s
apps (examples/app_p2p_DTR)	3m 23s
features (loco_tdoa3_all.conf)	4m 58s
apps (examples/app_stm_gap8_cpx)	3m 48s
apps (examples/demos/app_push_demo)	3m 50s
features (bigquad.conf)	4m 28s
apps (examples/demos/swarm_demo)	2m 36s
apps (examples/demos/app_wall_following_demo)	3m 36s
features (app_api.conf)	3m 35s
	1h 39m 1s

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