This is an inverse selection which excludes a selected set of targets
from the default target list. It will mostly be useful for CI
configurations but it might be useful for some users as well.

You cannot specify --target-list and --target-list-exclude at the same
time.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Tested-by: Wainer dos Santos Moschetta <wainersm@redhat.com>