Erro ao compilar - Ant e Eclipse

Buildfile: /home/workspace/MeuProjeto/build.xml
init:
     [echo] Criando o diret?rio de classes
clean:
     [echo] Limpando Classes
   [delete] Deleting directory /home/workspace/MeuProjeto/build
    [mkdir] Created dir: /home/workspace/MeuProjeto/build
compile:
     [echo] Compilando o projeto.
    [javac] Compiling 28 source files to /home/workspace/MeuProjeto/build
    [javac] /home/workspace/MeuProjeto/src/br/com/MeuProjeto/dominio/Clientes.java:5: package javax.persistence does not exist
    [javac] import javax.persistence.Column;
    [javac]                         ^
    [javac] /home/workspace/MeuProjeto/src/br/com/MeuProjeto/dominio/Clientes.java:6: package javax.persistence does not exist
    [javac] import javax.persistence.Entity;
    [javac]                         ^
    [javac] /home/workspace/MeuProjeto/src/br/com/MeuProjeto/dominio/Clientes.java:7: package javax.persistence does not exist
    [javac] import javax.persistence.Id;
    [javac]                         ^
    [javac] /home/workspace/MeuProjeto/src/br/com/MeuProjeto/dominio/Clientes.java:8: package javax.persistence does not exist
    [javac] import javax.persistence.Table;
    [javac]                         ^
    [javac] /home/workspace/MeuProjeto/src/br/com/MeuProjeto/dominio/Clientes.java:10: cannot find symbol
    [javac] symbol: class Entity
    [javac] @Entity
    [javac]  ^

<?xml version="1.0" encoding="iso-8859-1" ?>
<project name="MeuProjeto" default="compile" basedir=".">

	<property name="src" value="${basedir}\src" />
	<property name="build" value="${basedir}\build" />

	<target name="init">
		<echo>Criando o diretório de classes</echo>
		<mkdir dir="${build}" />
	</target>

	<target name="clean">
		<echo>Limpando Classes</echo>
		<delete dir="${build}" />
		<mkdir dir="${build}" />
	</target>

	<target name="compile" depends="init, clean" >
		<echo>Compilando o projeto.</echo>
		<javac fork="false" srcdir="\${src}" destdir="${build}" />
	</target>
</project>