Dub: A json/sdl equivalent to --combined command line option?

[Jon Degenhardt]

In Dub, is there a way to specify the equivalent of the 
--combined command line argument in the json/sdl package config 
file?

What I'd like to be able to do is create a custom build type such 
that

     $ dub build --build=build-xyz

builds in combined mode, without needing to add the --combined on 
the command line. Putting it on the command line as follows did 
what I intended:

    $ dub build --build=build-xyz --combined

--Jon