posix-configs: use '.' instead of 'source'

posix-configs/SITL/init/test/cmd_template.in

posix-configs/SITL/init/test/test_mavlink

posix-configs/SITL/init/test/test_template.in

posix-configs/SITL/init/test/tests_all

posix-configs/bbblue/px4.config

posix-configs/bbblue/px4_fw.config

posix-configs/bebop/px4.config

posix-configs/eagle/200qx/mainapp.config

posix-configs/eagle/210qc/mainapp.config

posix-configs/eagle/flight/mainapp.config

posix-configs/eagle/init/rcS

posix-configs/excelsior/mainapp.config

posix-configs/ocpoc/px4.config

posix-configs/rpi/px4.config

posix-configs/rpi/px4_fw.config

posix-configs/rpi/px4_hil.config

posix-configs/rpi/px4_no_shield.config