How to pass -J switch to compiler via DUB?

[fghost]

On Friday, 30 November 2018 at 11:05:26 UTC, Andrey wrote:
> Hi,
> How to pass -J switch to compiler via DUB?
> I want to import some text file at compile time:
>> string data = import("vertex.glsl");
>
> In dub.json:
> "dflags": [
>     "-J=vertex.glsl"
> ]
>
> The file itself is located on the same level as "dub.json".

The -J switch takes a directory path, not path to the file 
directly.