AVR build fixes

Makefile

@@ -78,13 +78,6 @@ test/packed_fs.c: Makefile src/ssi.h test/fuzz.c test/data/a.txt
 	$(CC) $(CFLAGS) test/pack.c -o pack
 	$(RUN) ./pack Makefile src/ssi.h test/fuzz.c test/data/a.txt test/data/range.txt > $@
 
-DIR ?= test/data
-OUT ?= packed_fs.c
-mkfs:
-	$(CC) $(CFLAGS) test/pack.c -o pack
-	$(RUN) ./pack -s $(DIR) `find $(DIR) -type f` > $(OUT)
-#	find $(DIR) -type f | sed -e s,^$(DIR),,g -e s,^/,,g
-
 # Check that all external (exported) symbols have "mg_" prefix
 mg_prefix: mongoose.c mongoose.h
 	$(CC) mongoose.c $(CFLAGS) -c -o /tmp/x.o && nm /tmp/x.o | grep ' T ' | grep -v 'mg_' ; test $$? = 1
@@ -165,17 +158,26 @@ arduino: ENV = -v $(CWD)/arduino:/root
 arduino:
 	curl -sL http://downloads.arduino.cc/arduino-1.8.19-linux64.tar.xz | unxz | tar -xf -
 	mv arduino-* $@
+
+arduino-xiao-board:
 	$(DOCKER) mdashnet/cc2 ./arduino/arduino --pref "boardsmanager.additional.urls=https://files.seeedstudio.com/arduino/package_seeeduino_boards_index.json" --save-prefs
 	$(DOCKER) mdashnet/cc2 ./arduino/arduino --pref "compiler.warning_level=all" --save-prefs
 	$(DOCKER) mdashnet/cc2 ./arduino/arduino --install-boards Seeeduino:samd
 
 arduino-xiao: ENV = -v $(CWD)/arduino:/root
-arduino-xiao: arduino
+arduino-xiao: arduino arduino-xiao-board
 	rm -rf tmp; mkdir tmp
 	cp examples/arduino/w5500/w5500.ino tmp/tmp.ino
 	cp mongoose.c mongoose.h examples/arduino/w5500/mongoose_custom.h tmp/
 	$(DOCKER) mdashnet/cc2 ./arduino/arduino --verbose --verify --board Seeeduino:samd:seeed_XIAO_m0 tmp/tmp.ino
 
+arduino-nano: ENV = -v $(CWD)/arduino:/root
+arduino-nano: arduino
+	rm -rf tmp; mkdir tmp
+	cp examples/arduino/w5500/w5500.ino tmp/tmp.ino
+	cp mongoose.c mongoose.h examples/arduino/w5500/mongoose_custom.h tmp/
+	$(DOCKER) mdashnet/cc2 ./arduino/arduino --verbose --verify --board arduino:avr:nano tmp/tmp.ino
+
 mingw++: Makefile mongoose.h $(SRCS)
 	$(DOCKER) mdashnet/mingw x86_64-w64-mingw32-g++ $(SRCS) -W -Wall -Werror -I. $(DEFS) -lwsock32 -o $@.exe