build-setup.sh: do not require DISTRO

In general, using the default DISTRO defined in the layer is what should
be tested in CI. gsj in fact requires this in order to fit with python3
now the default.

Change-Id: Ice618e1ccda7dbcaf1c8d07eb0f68ba3848718cf
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
1 file changed