feat: improve Makefile

Requiring setting the variables before building can avoid the situation
that, in the first time building, the default configurations are not what
users want.

Signed-off-by: Zhaoming Luo <[email protected]>

Author: LZhaoM

Makefile

@@ -1,21 +1,21 @@
 .PHONY: all build flash flash_spi clean distclean
 
-PRODUCT ?= c200
-# or airbox-orin
+PRODUCT = $(error Please set PRODUCT in Makefile)
+# c200 or airbox-orin
 
-PROFILE ?= Jetson
-# or JetsonMinimal
+PROFILE = $(error Please set PROFILE in Makefile)
+# Jetson or JetsonMinimal
 
-VARIANT ?= RELEASE
-# or DEBUG
+VARIANT = $(error Please set VARIANT in Makefile)
+# RELEASE or DEBUG
 
+BOARDSKU = $(error Please set BOARDSKU in Makefile)
 # 0000 - Jetson Orin NX 16GB
 # 0001 - Jetson Orin NX 8GB
 # 0003 - Jetson Orin Nano 8GB
 # 0004 - Jetson Orin Nano 4GB
 # 0005 - Jetson Orin Nano 8GB with SD card slot
 # See https://docs.nvidia.com/jetson/archives/r36.4.4/DeveloperGuide/index.html#devices-supported-by-this-document
-BOARDSKU ?= 0001
 
 # After compiling the modified dts file, the dtb file will appear under
 # `Linux_for_Tegra/source/kernel-devicetree/generic-dts/`, we need to put the