How to build plugin

Checkout the Groovy project from http://svn.jetbrains.org/idea/Trunk/groovy
Update to a new EAP of IntelliJ IDEA
When load a project for a first time set TEMPLATE variable to some directory inside the project
Select IntelliJ IDEA SDK as Project JDK
Add idea.jar from IDEA_HOME/lib to SDK classpath
Add tools.jar (for Windows) or classes.jar (for Mac) from your Java SDK directory to the current IntelliJ IDEA SDK classpath
Run generate.lexer task of ant buildfile build.xml placed in src directory of project
Run the make command from IDEA's Build menu
Run the Prepare Plugin Module 'groovy' for deployment command from IDEA's Build menu
A zip file will be generated in the project directory. Unzip it to the IDEA_HOME/plugins directory
Restart IDEA