Eclipse v4.7.1a: ant build broken: Launch configuration references non-existing project

Question

It seems that since eclipse v4.7.1a (fresh install), it is no more possible to execute any ant build. Each time it fails with the following messag

Answer 1

Yes, you're right, it's an Eclipse bug:

Eclipse bug 522581 - Cannot run ant build file from generic project

The bug was introduced in Oxygen.0 (4.7.0), probably by an update of the built-in Ant framework. A fix for this bug is scheduled for Oxygen.2 (4.7.2), December 20, 2017.

As already described by yourself in the question, Run in the same JRE as the workspace can be used as a workaround.