[Android] Compile module

Android 模組編譯(mm, mmm)

Invoke ". build/envsetup.sh" from your shell to add the following functions to your environment:

- 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.
- mmm: Builds all of the modules in the supplied directories.
- cgrep: Greps on all local C/C++ files.
- hgrep: Greps on all local C/C++ header files.
- jgrep: Greps on all local Java files.
- mkgrep: Greps on all local make files.
- rcgrep: Greps on all local .rc files.
- resgrep: Greps on all local res/*.xml files.
- shgrep: Greps on all local .sh files.
- godir: Go to the directory containing a file.

We can use mm/mmm to compile modules, don't need to build the whole system.