1 执行 Git add somefile 的时候，出现 如下 错误：
If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.
解决方法：
rm -f ./.git/index.lock
2. 编译ICS时 出现 如下错误：
build/core/Java.mk:20: *** dalvik/dexgen: Invalid LOCAL_SDK_VERSION '4' Choices are: current . Stop.
解决方法：
rm -rf prebuilt ; repo sync prebuilt