Building with Ant from Eclipse: "Specified VM install not found"

After an update of the JDK and successive removal of the old version, when I tried to build with Ant from Eclipse I got:

Specified VM install not found: type Standard VM, name jdk1.7.0_55

Yeah, right, OK, but where do I update the JDK that's used by Ant??
Here:
Run -> External Tools -> External Tools Configurations -> JRE

Thanks to Michael Borgwardt