Fix building and update build instructions

Makefile

@@ -89,6 +89,8 @@ OBJS_REL := $(patsubst $(OBJ_DIR)/%,%,$(OBJS))
 
 MAKEFLAGS += --no-print-directory
 
+AUTO_GEN_TARGETS :=
+
 all: rom
 
 rom: $(ROM)
@@ -117,6 +119,7 @@ clean: tidy
 	rm -f $(DATA_ASM_SUBDIR)/layouts/layouts.inc $(DATA_ASM_SUBDIR)/layouts/layouts_table.inc
 	rm -f $(DATA_ASM_SUBDIR)/maps/connections.inc $(DATA_ASM_SUBDIR)/maps/events.inc $(DATA_ASM_SUBDIR)/maps/groups.inc $(DATA_ASM_SUBDIR)/maps/headers.inc
 	find $(DATA_ASM_SUBDIR)/maps \( -iname 'connections.inc' -o -iname 'events.inc' -o -iname 'header.inc' \) -exec rm {} +
+	rm -f $(AUTO_GEN_TARGETS)
 	@$(MAKE) clean -C berry_fix
 	@$(MAKE) clean -C tools/gbagfx
 	@$(MAKE) clean -C tools/scaninc