怎么单独build android ap (以launcher为例)

如何单独build android ap (以launcher为例)
单独build launcher.
$cd <ANDROID>
$export TOP='pwd'
$source build/envsetup.sh
$cd packages/apps/Launcher
$mm

将build出来的launcher.apk push到SDK当中
$adb push out/..../system/app/Launcher.apk /system/app
$adb shell stop zygote
$adb shell start zygote