This means that multiple builds will not conflict, so we can
remove the lock from the CI. Also quieter when no errors.
Some still left to do, only done the ones used in build and CI
initially. Some of the others will be cleaned up anyway later.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Linux xargs calls the command with no arguments if it gets no inputs, which
`docker rmi` complains about. It provides -r / --no-run-if-empty to prevent
this but unfortunately this isn't supported on OSX.
Ignore errors from `docker rmi` so that `make clean` will keep going and clean
up later stuff.
Signed-off-by: Ian Campbell <ian.campbell@docker.com>
