makefile for android build

makefile depends

<android source root>/Makefile {
  build/core/main.mk {
    build/core/config.mk {
      build/core/envsetup.mk
        build/core/product_config.mk => product.mk ==> AndroidProducts.mk ==> TARGET_DEVICE
      BoardConfig.mk ==> TARGET_CPU_ABI
    }
    include $(BYUILD_SYSTEM)/Makefile
  }
}

根據上述的引入順序，AndroidProducts.mk 先載入，BoardConfig,mk 才載入

-include <file> ## 無論include過程中出現甚麼錯誤，都不要報錯繼續執行。
TOPDIR == <android source root>/
BUILD_SYSTEM ==  <android source root>/build/core/

export OUT_DIR=<your out folder> ##可以設定你所想要產生的位置

must have only one BoardConfig.mk in whole build environment  ## config.mk  line#129