build command in android

voke ". build/envsetup.sh" from your shell to add the following functions to your environment:
   lunch:   lunch -<build_variant>
   tapas:   tapas [<App1> <App2> ...] [arm|x86|mips|armv5] [eng|userdebug|user]
   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, but not their dependencies.
   mmm:     Builds all of the modules in the supplied directories, but not their dependencies.
            To limit the modules being built use the syntax: mmm dir/:target1,target2.
   mma:     Builds all of the modules in the current directory, and their dependencies.
   mmma:    Builds all of the modules in the supplied directories, and their dependencies.
   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.

cd ~/android/source
source build/envsetup.sh
lunch      # <- (choose your device from the list)

# To build .img files of the platform (you will need to 'fastboot' these onto a device that supports fastboot):
make

# To build an OTA (Over The Air) package (zip files that carriers send out to devices for updates):
make otapackage

# To build a specific component, for example the Camera application:
make Camera

http://xda-university.com/as-a-developer/getting-started-building-android-from-source