Add `--parallel` to `docker build`'s options in `bash` and `zsh` completion

Signed-off-by: Ulysses Souza <ulysses.souza@docker.com>

contrib/completion/bash/docker-compose

@@ -114,7 +114,7 @@ _docker_compose_build() {
 
 	case "$cur" in
 		-*)
-			COMPREPLY=( $( compgen -W "--build-arg --compress --force-rm --help --memory --no-cache --pull" -- "$cur" ) )
+			COMPREPLY=( $( compgen -W "--build-arg --compress --force-rm --help --memory --no-cache --pull --parallel" -- "$cur" ) )
 			;;
 		*)
 			__docker_compose_complete_services --filter source=build

contrib/completion/zsh/_docker-compose

@@ -117,6 +117,7 @@ __docker-compose_subcommand() {
                 '--no-cache[Do not use cache when building the image.]' \
                 '--pull[Always attempt to pull a newer version of the image.]' \
                 '--compress[Compress the build context using gzip.]' \
+                '--parallel[Build images in parallel.]' \
                 '*:services:__docker-compose_services_from_build' && ret=0
             ;;
         (bundle)