VS-RK3288板卡 Android7.1编译流程
make调用build/core/main.mk产生各种目标文件：# Build files and then package it into the rom formats
.PHONY: droidcore
droidcore: files \
systemimage \
$(INSTALLED_BOOTIMAGE_TARGET) \
$(INSTALLED_RECOVERYIMAGE_TARGET) \
$(INSTALLED_USERDATAIMAGE_TARGET) \
$(INSTALLED_CACHEIMAGE_TARGET) \
$(INSTALLED_VENDORIMAGE_TARGET) \
$(INSTALLED_SYSTEMOTHERIMAGE_TARGET) \
$(INSTALLED_FILES_FILE) \
$(INSTALLED_FILES_FILE_VENDOR) \
$(INSTALLED_FILES_FILE_SYSTEMOTHER)
最终使用make_ext4fs产生镜像文件：
make_ext4fs -s -T -1 -S out/target/product/rk3288/root/file_contexts.bin -L system -l 2147483648 -a system out/target/product/rk3288/obj/PACKAGING/systemimage_intermediates/system.img out/target/product/rk3288/system out/target/product/rk3288/system