android源码目录下的build/envsetup.sh文件，描述编译的命令
- m: Makes from the top of the tree.
- mm: Builds all of the modules in the current directory.
- mmm: Builds all of the modules in the supplied directories.
要想使用这些命令，首先需要在android源码根目录执行. build/envsetup.sh 脚本设置环境
m：编译所有的模块
mm：编译当前目录下的模块，当前目录下要有Android.mk文件
mmm：编译指定路径下的模块，指定路径下要有Android.mk文件
下面举个例子说明，假设我要编译android下的\hardware\libhardware_legacy\power模块，当前目录为源码根目录，
方法如下：
1、. build/envsetup.sh
2、mmm hardware/libhardware_legacy/power/
或者 ：
1、. build/envsetup.sh
2、cd hardware/libhardware_legacy/power/
3、mm
++++++++++++++++++++++++++++
[root@localhost build]# . envsetup.sh
执行完后，就会多出以下几个命令：
- croot: Changes directory to the top of the tree.
- m: Makes from the top of the tree.
- mm: Builds all of the modules in the current directory. 用于当前目录下的工程
- mmm: Builds all of the modules in the supplied directories. 用于编译指定目录，如：mmm Settings，表示编译Settings这个目录，之后会生成新的apk
- cgrep: Greps on all local C/C++ files.
- jgrep: Greps on all local Java files.
- resgrep: Greps on all local res/*.xml files.
- godir: Go to the directory containing a file.
- printconfig: 当前build的配置情况
