You can use localconf.mk to remember your own make options, such as TARGET and different ENA flags, without editing the distributed Makefile.
One useful option to put in localconf.mk is ENA_GEN which will turn on the dependencies that will trigger generation of the files in zxid/c directory. For example
echo 'ENA_GEN=1' >>localconf.mk make
WARNING: If you are confused about compilation flags appearing "out of nowhere", despite not being mentioned in the Makefile, be sure you have not inadvertently created a localconf.mk (perhaps you rsynced the sources from another machine and forgot to remove localconf.mk). A similar problem can occur if you accidentally copied deps.dep from another machine. It will reference the dependencies with the paths of that machine. Just remove the deps.dep to solve this issue.