feat: simplified Makefile build with SDK submodule

.gitignore

@@ -1,2 +1,3 @@
 output/**
 **/*.o
+/custom.mk

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "sdk"]
+	path = sdk
+	url = https://github.com/openshwprojects/OpenBK7231T.git

Makefile

@@ -0,0 +1,52 @@
+# HACK - if COMPILE_PREX defined then we are being called running from original build_app.sh script in standard SDK
+# Required to not break old build_app.sh script lines 74-77
+ifdef COMPILE_PREX
+all:
+	@echo Calling original build_app.sh script
+	cd $(PWD)/../../platforms/$(TARGET_PLATFORM)/toolchain/$(TUYA_APPS_BUILD_PATH) && sh $(TUYA_APPS_BUILD_CMD) $(APP_NAME) $(APP_VERSION) $(TARGET_PLATFORM)
+else
+
+######## Continue with custom simplied Makefile ########
+
+# Use current folder name as app name
+APP_NAME ?= $(shell basename $(CURDIR))
+# Use current timestamp as version number
+TIMESTAMP := $(shell date +%Y%m%d_%H%M%S)
+APP_VERSION ?= dev_$(TIMESTAMP)
+
+TARGET_PLATFORM ?= bk7231t
+APPS_BUILD_PATH ?= ../bk7231t_os
+APPS_BUILD_CMD ?= build.sh
+
+# Default target is to run build
+all: build
+
+# Full target will clean then build all
+.PHONY: full
+full: clean build
+
+# Update/init git submodules
+.PHONY: submodules
+submodules:
+	git submodule update --init --recursive
+
+# Create symlink for App into SDK folder structure
+sdk/apps/$(APP_NAME):
+	@echo Create symlink for $(APP_NAME) into sdk/apps folder
+	ln -s "$(shell pwd)/" "sdk/apps/$(APP_NAME)"
+
+# Build main binary
+.PHONY: build
+build: submodules sdk/apps/$(APP_NAME)
+	cd sdk/platforms/$(TARGET_PLATFORM)/toolchain/$(APPS_BUILD_PATH) && sh $(APPS_BUILD_CMD) $(APP_NAME) $(APP_VERSION) $(TARGET_PLATFORM)
+
+# clean .o files
+.PHONY: clean
+clean: 
+	$(MAKE) -C sdk/platforms/$(TARGET_PLATFORM)/toolchain/$(APPS_BUILD_PATH) APP_BIN_NAME=$(APP_NAME) USER_SW_VER=$(APP_VERSION) clean
+	rm -rf output/*
+
+# Add custom Makefile if required
+-include custom.mk
+
+endif