rls is extra_excluded in debian rules file:
# extra modules to skip, because they are not compilable now
# - regardless if they go to the main kamailio package or to some module
package,
# they will be excluded from compile and install of all
EXTRA_EXCLUDED_MODULES=bdb dbtext oracle pa rls iptrtpproxy
I tested and modules_k/rls compiles fine. I think the above text is true
only for ser's version.
regards
Klaus