JDK-8015656 changes behavior of the collections in a way that breaks antlr. It turns out that this affects both our ant build and our gradle build, but the ant build didn't notice because it *did not fail the build* if the antlr call failed, whereas the gradle build did.

We can "fix" the gradle build by causing it to also ignore this error. It so happens that the antlr failure occurs after the source files have all been generated, so we are able to continue building even with this bug. Of course, after JDK-8015656 is fixed, we ought to undo this so that if the antlr call fails, we are notified of this.