Setting up ant (Linux Mint)

Install ANT

sudo apt-get install ant

Create Ant build files 

xxxx@xxxx ~/abc/Code/StorageWidget $ ~/android/android-sdk-linux/tools/android update project --path .
Updated local.properties
No project name specified, using Activity name 'HelpTopicActivity'.
If you wish to change it, edit the first line of build.xml.
Added file ./build.xml
It seems that there are sub-projects. If you want to update them
please use the --subprojects parameter.

the sdk.dir is added in local.properties correctly, but somehow the ant doesn't use it when building. Have to add the env variable ANDROID_HOME for now.

export ANDROID_HOME=/path/to/android-sdk-linux/

or

ant debug -Dsdk.dir=$ANDROID_HOME

Reference

http://www.androidengineer.com/2010/06/using-ant-to-automate-building-android.html
https://developer.android.com/tools/projects/projects-cmdline.html#UpdatingAProject

Quick summary