extend WANT_SYSTEM_LUA=1 to other distros

Only tested on Ubuntu at this point.

feedback on other distros is welcome

sys/unix/Makefile.top

@@ -127,8 +127,9 @@ LUATOP ?= $(LUAHEADERS)
 LUAMAKEFLAGS ?= CC='$(CC)' SYSCFLAGS='$(SYSCFLAGS)'
 LUA2NHTOP ?= ../../..
 LUABASELIB ?= liblua-$(LUA_VERSION).a
-TOPLUALIB ?= lib/lua/$(LUABASELIB)
+LUATOPLIB ?= lib/lua/$(LUABASELIB)
 LUAHPREFIX ?= ../
+LUALIBBUILT ?= $(LUATOP)/liblua.a
 
 ALLDEP = $(PRECHECK) $(GAME) recover Guidebook $(VARDAT) spec_levs check-dlb
 
@@ -144,11 +145,11 @@ lua_support: include/nhlua.h
 	@true
 $(LUATOP)/liblua.a: $(LUAHEADERS)/lua.h
 	( cd $(LUATOP) && make $(LUAMAKEFLAGS) a )
-$(TOPLUALIB): $(LUATOP)/liblua.a
+lib/lua/$(LUABASELIB): $(LUALIBBUILT)
 	@( if test -d lib/lua ; then true ; else mkdir -p lib/lua ; fi )
 	cp $(LUATOP)/liblua.a $@
 
-include/nhlua.h: $(TOPLUALIB)
+include/nhlua.h: $(LUATOPLIB)
 	echo '/* nhlua.h - generated by top Makefile */' > $@
 	@echo '#include "$(LUAHPREFIX)$(LUAHEADERS)/lua.h"' >> $@
 	@sed -e '/(lua_error)/!d' \