Global domain config for unique GC log file name and path

Customers often try to do something like the following in their server group for domain mode to easily get a unique gc log path for all server group members:

<option value="-Xloggc:${jboss.server.log.dir}/gc.log"/>

But jboss.server.log.dir can't be resolved at that point so it fails. The next best thing that can be done is:

<option value="-Xloggc:${jboss.domain.servers.dir}/server-name/log/gc.log"/>

But then that has to be set for each server. It'd help if domain mode had some way of easily setting a gc.log path in a server-group level or higher that could be set once and result in unique gc log paths for all servers in the server-group.