How to add a ssl server cert for groovy?

I work behind a firewall, and it requires that I add a cert for our proxy
to the cacerts file in the Java distribution. This works fine.

I have a quite old version of Groovy installed on my desktop, v2.4.21,
which is the version used by our Jenkins pipeline script.  I want to test
some code in groovyConsole before I try to run it on our CI server. For
many things, this works fine. However, I'm trying to iterate on some code
that makes a https connection, and I'm getting an error in groovyConsole
that I believe is the same error I get when the server cert is missing
("PKIX path building failed"), which isn't surprising because I never
installed the root cert in the Groovy distribution.

I've never really looked inside the Groovy distribution before. I don't
even see a cacerts file or anything that really looks like it, so it must
do this in a different way than the Java distribution. Is it possible that
this is because I'm using such an old version of Groovy?