Resolve dub dependency

[JN]

I am trying to use bindbc-sdl and bindbc-wgpu at the same time. 
The error is:

Unresolvable dependencies to package bindbc-loader:
   bindbc-sdl 0.19.1 depends on bindbc-loader ~>0.3.0
   bindbc-sdl 0.19.1 depends on bindbc-loader ~>0.3.0
   bindbc-wgpu 0.1.0-alpha8 depends on bindbc-loader ~>0.2.1

What is the cleanest way to resolve this? I don't understand why 
can't -sdl and -wgpu use different versions of the loader library.