buildroot

python3: remove full path from .pyc

.pyc files include path to source .py file. This patch changes the way
`pycompile.py' is launched in order to only keep the part relative to
$TARGET_DIR.

This work was sponsored by `BA Robotic Systems'.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>