本想嵌入式開發作爲一個業餘愛好低調進行，但是遇到了一個問題問度娘，居然沒有答案。
依然只好求救於google Google
已經退出中國市場——你懂得！所以爲了方便大家，只好把答案貼出來：
問題如題：
you really meant source build/envsetup.sh right?
If not, that is likely the cause of your problems.
你確定你是否真正的執行了 source
build/envsetup.sh 進入瞭解壓andorid 源碼的文件夾之後執行也許大部分小白
（我也是小白） 就像我和這位大佬美一樣 ：
I went and pulled the Android Source and and
synced it. All was swell. Next up was to run:
envsetup.sh