This makes makesyscalls.lua more parallel-friendly, or at least not as hostile to the idea. We get into situations where we're running parallel if we end up with MAKE_JOBS>1 entering any of the sysent targets, since each output file is recognized a distinct build step that needs to be executed. Another commit will add some .ORDER to further improve the situation. Reported by: jhb Reviewed by: brooks Differential Revision: https://reviews.freebsd.org/D23098