Enhance esp32 makefile

examples/esp32/device-dashboard/Makefile

@@ -1,5 +1,7 @@
 THISDIR = $(realpath $(CURDIR))
 ROOTDIR = $(realpath $(CURDIR)/../../..)
+DOCKER ?= docker run --rm $(DA) -v $(ROOTDIR):$(ROOTDIR) -w $(THISDIR) espressif/idf
+CMD ?= idf.py build
 
 all: example
 
@@ -7,7 +9,7 @@ example:
 	true
 
 build: main/main.c Makefile
-	docker run --rm -v $(ROOTDIR):$(ROOTDIR) -w $(THISDIR) espressif/idf idf.py build
+	$(DOCKER) $(CMD)
 
 COMPORT ?= /dev/cu.SLAB_USBtoUART
 ESPTOOL ?= esptool.py
@@ -15,4 +17,4 @@ flash:
 	cd build && $(ESPTOOL) --chip esp32 -p $(COMPORT) -b 460800 --before=default_reset --after=hard_reset write_flash --flash_mode dio --flash_freq 40m --flash_size 2MB 0x8000 partition_table/partition-table.bin 0x1000 bootloader/bootloader.bin 0x100000 mongoose-esp32-example.bin
 
 clean:
-	rm -rf build
+	$(DOCKER) rm -rf build sdkconfig