Maintenance: Speed up custom overcommit hook.

.overcommit.sh

@@ -1,11 +1,19 @@
 #!/bin/bash
 
-set -eux
+set -eu
 
 # Don't require redis.
 export ZAMMAD_SAFE_MODE=1
 
 echo "Checking .pot catalog consistency..."
-rails generate zammad:translation_catalog --check
+rails generate zammad:translation_catalog --check &
 
-.gitlab/check_graphql_api_consistency.sh
+.gitlab/check_graphql_api_consistency.sh &
+
+FAILED=0
+for job in $(jobs -p)
+do
+  wait $job || let "FAILED+=1"
+done
+
+exit $FAILED