esp32: make sure esp32/max80/src actually exists

esp32/Makefile

@@ -39,6 +39,7 @@ $(TARGET): $(shell find $(SKETCH) -type f) $(GENFILES) $(common)
 		$(ARDUINO_CLI) compile $(ARDUINO_OPTS)
 
 $(common):
+	mkdir -p $(@D)
 	cd $(@D) && ln -sf ../../../common .
 
 .PHONY: zip