/usr/ports/shells/es builds but does not run on amd64/FBSD 6.  
 
mksignal tries to build some definitions, but at least for my system adds
too many and runs afoul of the check in signals.c
In particular, SIGLWP == NSIG
 
Note:
 /sys/signal.h:#define  SIGLWP          SIGTHR
and SIGTHR was already a problem.

Fix: 

The following is a diff against the original mksignal, and fixes the problem
addressed by patch-mksignal -- it is a replacement. I just added 2 lines
that do a check against NSIG when defining signals. This seems better to
me than just adding ignores as it's general -- it will still work if the
signals get renumbered (as they apparently were).
 
 --- patch-mksignal2 begins here ---
 --- mksignal.orig    Mon Jan  2 19:28:47 2006
 +++ mksignal    Sat Jan  7 17:52:43 2006
 @@ -141,7 +141,9 @@
                  lcname = lcname c
              }
              print "#ifdef", signal
 +            print "#if ", signal, " < NSIG"
              printf "\t{ %s,\t\"%s\",\t\"%s\" },\n", signal, lcname, mesg[signal]
 +            print "#endif"
              print "#endif"
          }
      }
 --- patch-mksignal2 ends here ---
How-To-Repeat: Just try to run :
 celeborn.my.domain{sam} > ./es
 es panic: initsignals: bad signal in sigmsgs.c: siglwp (see mksignal)