今天在看MTK提供的SDK编译文档，按照步骤做，结果出错了，文档如下：

2- Building an SDK for MacOS and Linux
--------------------------------------

First, setup your development environment and get the Android source code from
git as explained here:

  http://source.android.com/source/download.html

For example for the cupcake branch:

  $ mkdir ~/my-android-git
  $ cd ~/my-android-git
  $ repo init -u https://android.googlesource.com/platform/manifest -b master -g all,-notdefault,tools
  $ repo sync

Then once you have all the source, simply build the SDK using:

  $ cd ~/my-android-git
  $ . build/envsetup.sh
  $ lunch sdk-eng          这个sdk-eng指的是对应的mtk版本
  $ make sdk

This will take a while, maybe between 20 minutes and several hours depending on
your machine. After a while you'll see this in the output:

  Package SDK: out/host/darwin-x86/sdk/android-sdk_eng.<build-id>_mac-x86.zip

Some options:

- Depending on your machine you can tell 'make' to build more things in
  parallel, e.g. if you have a dual core, use "make -j4 sdk" to build faster.

- You can define "BUILD_NUMBER" to control the build identifier that gets
  incorporated in the resulting archive. The default is to use your username.
  One suggestion is to include the date, e.g.:

  $ export BUILD_NUMBER=${USER}-`date +%Y%m%d-%H%M%S`

  There are certain characters you should avoid in the build number, typically
  everything that might confuse 'make' or your shell. So for example avoid
  punctuation and characters like $ & : / \ < > , and .

em_t8370_emmc,所以我的sdk名字就是em_t8370_emmc，看来文档有时会让人产生误解的啊，还好是老一辈的总工告诉了我，不然我还蒙在谷里呢！！今天总算知道了，呵呵呵。

然后，说说我遇到的问题和如何解决的方法吧：

1、按照源码中sdk目录下的howto_build_SDK.txt参考文档的编译方式
  $ cd ~/my-android-git
  $ . build/envsetup.sh
  $ lunch sdk-eng         
  $ make sdk
 结果,产生错误log信息如下：
 device/mediatek/build/build/libs/custom.mk:159: PWD = /mnt/sdb1/yangyx/MT8127_M0_MP8_0407
 device/mediatek/build/build/libs/custom.mk:160: *** Can not find ProjectConfig.mk , MTK_PROJECT_CONFIGS = .  Stop.

#### make failed to build some targets (48 seconds) ####
 
 
2、根据一些参考资料，我解决以上相关问题采用以下步骤:
	source build/envsetup
	lunch em_t8370_emmc-user
	source build/envsetup    #需要重新source一次，我也不知道为什么，如果不重新再执行这句话，编译还是会产生像上面一样的问题。
	make sdk
	结果，产生的错误log信息如下：
	Package SDK: out/host/linux-x86/sdk/em_t8370_emmc/android-sdk_1476082019_linux-x86.zip
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libexif.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2_blkid.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2_com_err.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2_e2p.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2_profile.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2_quota.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2_uuid.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libext2fs.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libiprouteutil.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libnetlink.so
	SDK: warning: including GNU target out/target/product/em_t8370_emmc/system/lib/libnl.so
	development/build/sdk.atree:49: couldn't locate source file: bin/etc1tool
	development/build/sdk.atree:88: couldn't locate source file: bin/split-select
	development/build/sdk.atree:93: couldn't locate source file: bin/bcc_compat
	development/build/sdk.atree:186: couldn't locate source file: framework/layoutlib.jar
	development/build/sdk.atree:525: couldn't locate source file: framework/layoutlib-tests.jar
	development/build/sdk.atree:526: couldn't locate source file: system/app/EmulatorSmokeTests/EmulatorSmokeTests.apk
	make: *** [out/host/linux-x86/sdk/em_t8370_emmc/android-sdk_1476082019_linux-x86.zip] Error 44

3、注释以上sdk.atress 49 88 93 186 525 526 相关的脚本 
   编译成功，在相关目录下生成以下的文件:
   Package SDK: out/host/darwin-x86/sdk/android-sdk_eng.<build-id>_mac-x86.zip
   生成的android.jar是最新的:
   /out/host/linux-x86/sdk/em_t8370_emmc/android-sdk_1476083189_linux-x86/platforms/android-6.0/android.jar