Make J configurable

builder.sh

@@ -57,7 +57,9 @@ DEBUG="V=s"
 PRIO=0
 
 # how parallel do you want to build?
-J=10
+if [ -z "${J}" ]; then
+	J=10
+fi
 
 # prepare site.conf from template
 if [ -f site/site.conf ]; then