Remove useless variable

Signed-off-by: Kévin THIERRY <kevin.thierry@open.eurogiciel.org>
Add Wayland and Weston to .spec2yoctorc

Also replace hard-coded paths in .spec2yoctorc with the environment
variable YOCTO_WORKDIR.

Signed-off-by: Kévin THIERRY <kevin.thierry@open.eurogiciel.org>
Update README.md

Signed-off-by: Kévin THIERRY <kevin.thierry@open.eurogiciel.org>