How does the D compiler get updated on travis-ci.org?

[Gary Willoughby via Digitalmars-d]

Now that we have a new D compiler version released how does the D 
compiler on travis-ci.org get updated?

I've recently fixed some issues (in my code) that were hampered 
by a bug in the last version. Now that it's fixed the older 
version on travis-ci.org is crashing because of it.

I've raised an issue here:
https://github.com/travis-ci/travis-ci/issues/3472