The real message is that Ant can’t find com.sun.tools.javac.Main.
Which, together with the fact that the latest “Sun” (Oracle) JDK is 1.7.0_13 (or maybe _14, but definitely not the “_52” that your install dir indicates), makes me think that you’re not using a distribution that Ant recognizes. You can verify this by running jar tvf $JAVA_HOME/lib/tools.jar, and looking for that class.
The Ant Manual talks about ways to work with different compilers. Since I’ve only used “Sun” compilers, I’m afraid that I can’t give you any pointers.
Edit: you could also try setting fork="yes" in your build file. This should run the compiler executable rather than trying to invoke the compiler class.
