layer.conf: fix parse
layer.conf: fix parse

after meta-systemd commit [1] the following error was thrown during parsing:

ERROR: Unable to parse /home/Superandy/data/oe-core/sources/meta-raspberrypi/conf/layer.conf:
Failure expanding variable BBFILES, expression was
...
which triggered exception NameError: name 'base_contains' is not defined

[1] http://cgit.openembedded.org/meta-openembedded/commit/?id=3c21a46020bd0816579648f684c41dbd6333583e

Signed-off-by: Andreas Müller <d72a15aaaca3a7afa855175c72dc8d2e05931e32@googlemail.com>
Signed-off-by: Andrei Gherzan <8dc7c09356db0b1762fb140617d7375c0a5a4131@gherzan.ro>

sarnold/meta-alt-desktop-extras,sarnold/meta-alt-desktop-extras,sarnold/meta-alt-desktop-extras