By default if IoT-LAB Cli Tools V3 is used then BINFILE is used to
flash on IoT-LAB. But BINFILE is not built by default when RIOT_CI_BUILD
is set as a ci optimization.
But since before IOTLAB_NODE was not passed to docker when building it
did not know that it should BUILD BINFILE as well, which led to failures
if doing:
$ IOTLAB_NODE=iotlab-m3.grenoble.iot-lab.info BOARD=iotlab-m3 \
RIOT_CI_BUILD=1 BUILD_IN_DOCKER=1 make -C examples/hello-world/ flash
But if IOTLAB_NODE is passed at is checks for IoT-LAB cli Tools also
happen in the docker container which leads to a make error since those
are not present in docker.
Therefore add BINFILE to BUILD_FILES if RIOT_CI_BUILD is set, but unset
IOTLAB_NODE once INSIDE_DOCKER.
