TOOLS-74: allow Makefile.targ projects to have additional 'clean' target rules
TOOLS-74: allow Makefile.targ projects to have additional 'clean' target rules

joyent/eng,joyent/sdc-net-agent,joyent/sdc-agents-core,joyent/sdc-net-agent,joyent/sdc-provisioner-agent,joyent/sdc-heartbeater-agent,joyent/sdc-hagfish-watcher,joyent/eng,joyent/eng,joyent/sdc-agents-core,joyent/sdc-vm-agent,joyent/sdc-heartbeater-agent,joyent/sdc-hagfish-watcher,joyent/eng,joyent/sdc-vm-agent,joyent/eng,joyent/sdc-provisioner-agent