contents of my build.xml

build.xml

<?xml version="1.0"?> 
<project default="release">  

    <target name="release"> 
        <echo>
        	Building release build
        </echo> 
        <fb.exportReleaseBuild project="Amazing Project" /> 
    </target> 
    
</project>

console output

[........]ant/build.xml:8: Problem: failed to create task or type fb.exportReleaseBuild
Cause: The name is undefined.
Action: Check the spelling.
Action: Check that any custom tasks/types have been declared.
Action: Check that any <presetdef>/<macrodef> declarations have taken place.