I.MX6 system.img unpack repack

/*************************************************************************
 *                 I.MX6 system.img unpack repack
 * 说明：
 *     以前的system.img直接ext4的，现在的system.img是data类型的，需要工具
 * 进行转换才行，需要这些工具主要是还是为了减少开发中编译等待时间过长。
 *
 *                                     2016-9-10 深圳 南山平山村 曾剑锋
 ************************************************************************/

一、参考文档：
    1. Android中system.img的两种格式及其相互转换方法
        http://www.th7.cn/Program/Android/201501/381202.shtml
    2. ext4 unpack/repack tools
        http://web.djodjo.org/article/download/android/tools/x86_linux/ext4tools

二、执行命令：
    1. source ./build/envsetup.sh 
    2. make img2simg_host

三、编译输出信息：
    ......
    including ./system/security/softkeymaster/Android.mk ...
    including ./system/vold/Android.mk ...
    including ./tools/external/fat32lib/Android.mk ...
    *** Overlay change detected, clean shared intermediate files...
    *** rm -rf out/target/common/obj/APPS/framework-res_intermediates out/target/common/obj/APPS/Launcher2_intermediates out/target/common/obj/APPS/SettingsProvider_intermediates out/target/common/obj/APPS/Settings_intermediates out/target/common/obj/APPS/Bluetooth_intermediates
    Import includes file: out/host/linux-x86/obj32/EXECUTABLES/img2simg_host_intermediates/import_includes
    Header: out/target/product/generic/obj/include/libexpat/expat.h
    Header: out/target/product/generic/obj/include/libexpat/expat_external.h
    Header: out/target/product/generic/obj/include/libpng/png.h
    Header: out/target/product/generic/obj/include/libpng/pngconf.h
    Header: out/target/product/generic/obj/include/libpng/pngusr.h
    Header: out/target/product/generic/obj/include/selinux/selinux.h
    Header: out/target/product/generic/obj/include/selinux/label.h
    Header: out/target/product/generic/obj/include/selinux/context.h
    Header: out/target/product/generic/obj/include/selinux/avc.h
    Header: out/target/product/generic/obj/include/selinux/android.h
    Header: out/target/product/generic/obj/include/libsonivox/eas.h
    Header: out/target/product/generic/obj/include/libsonivox/eas_types.h
    Header: out/target/product/generic/obj/include/libsonivox/eas_reverb.h
    Header: out/target/product/generic/obj/include/libsonivox/jet.h
    Header: out/target/product/generic/obj/include/libsonivox/ARM_synth_constants_gnu.inc
    Header: out/target/product/generic/obj/include/libwpa_client/wpa_ctrl.h
    Header: out/target/product/generic/obj/include/libwpa_client/qca-vendor.h
    host C: img2simg_host <= system/core/libsparse/img2simg.c
    Export includes file: system/core/libsparse/Android.mk -- out/host/linux-x86/obj32/EXECUTABLES/img2simg_host_intermediates/export_includes
    host Executable: img2simg_host (out/host/linux-x86/obj32/EXECUTABLES/img2simg_host_intermediates/img2simg)
    Install: out/host/linux-x86/bin/img2simg

#### make completed successfully (03:18 (mm:ss)) ####

    zengjf@zengjf:~/myandroid$ 

四、真正的img2simg
    1. 上面编译出来的img2simg还是有问题，会报如下错误：
        zengjf@zengjf:~/myandroid$ img2simg out/target/product/sabresd_6dq/obj/PACKAGING/systemimage_intermediates/system.img system.img
        img2simg: ../../core/libsparse/sparse.c:143: write_all_blocks: Assertion `pad >= 0' failed.
        Aborted (core dumped)
    2. 下载参考文档中的img2simg，验证可行。