Run the test-sigjmp program as a separate task.

scripts/xenofarm.sh

@@ -179,6 +179,7 @@ dotask 0 "fds"    "" "cd $BASE/src/server/testsuite && make check-testfd"
 dotask 0 "id_cc"  "" "cd $BASE && make ident-cc"
 dotask 0 "id_tx"  "" "cd $BASE/doc && make ident-makeinfo"
 dotask 1 "make"   "makewarn" "cd $BASE && make $makeargs"
+dotask 0 "sigjmp" "" "cd $BASE/src/server/testsuite && make check-test-sigjmp"
 
 #
 # "make check" requirements