Fuzztest installs antlr into the source folder

Discovered this while building fuzztest using cmake. In the root of my project a `dist` folder appeared with libantlr. This seems to be an outcome of this issue: https://github.com/antlr/antlr4/issues/3784

Unfortunately antlr-cpp enables building tests by default, so fuzztest needs to explicitly turn off antlr-cpp building its own tests. (It should also disable building the shared library, since this is unused.)

I'd be happy to provide a PR, although I suppose I would have to sign the CLA first?