scripts: fix installing samples

It's been a while now that the working directory CT_WORK_DIR has
been changed from 'targets' to '.build'. Fix the install procedure
to properly tweak the installed samples.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

reporter_name="Thomas Petazzoni"

reporter_url="http://www.free-electrons.com/"

reporter_comment="Very basic testing only"