LuaJIT: make distclean -> make clean

Two reasons for this change:

1. The latest LuaJIT has no "distclean" target
2. The "distclean" is MUCH slower

Makefile

@@ -210,7 +210,7 @@ clean:
 	rm -f *.o kpdfview slider_watcher
 
 cleanthirdparty:
-	$(MAKE) -C $(LUADIR) CC="$(HOSTCC)" CFLAGS="$(BASE_CFLAGS)" distclean
+	$(MAKE) -C $(LUADIR) CC="$(HOSTCC)" CFLAGS="$(BASE_CFLAGS)" clean
 	$(MAKE) -C $(MUPDFDIR) build="release" clean
 	$(MAKE) -C $(CRENGINEDIR)/thirdparty/antiword clean
 	test -d $(CRENGINEDIR)/thirdparty/chmlib && $(MAKE) -C $(CRENGINEDIR)/thirdparty/chmlib clean || echo warn: chmlib folder not found