E3-574: Fixing the .dbd install issue

The problem here was the way that DBDCAT as a variable works: it generates a new .dbd file in the target install location based on the contents of that variable, and hence our issue.

However, this isn't the right way for us to use the build system; we know in advance that we will just include all of the devEpics.dbd files, so we may as well include them straightaway.