scripts: fix default work-dir name

It's been a long time the default work-dir changed its name
from 'target' to '.build'.

Change the left-over.

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

 reporter_name="Esben Haabendal"

 reporter_url="esben@haabendal.dk"

 reporter_comment="Example for building a toolchain for m68k no-mmu Linux targets"