Make Dub output *.di files

[bitwise]

On Saturday, 9 March 2019 at 18:39:29 UTC, bitwise wrote:
> Is it possible to get Dub to output import headers for compiled 
> D files?

I found this, which almost works:

"dflags": [ "-H", "-Hdimport", "-op" ]

The only problem is that Dub runs *above* the source directory, 
resulting in all my import files being nested in /source/..

So can I get Dub to run the compilation from the /source 
directory instead?

Or is there a way to tell Dub to generate the headers for each 
file some other way?