dub: Generate Ninja/make targets for all matching configurations by default?

[kinke]

Right now, the default reggaefile.d works fine for simple projects. But as soon as a non-default configuration or multiple configurations are to be built, a custom file and boilerplate is necessary. I think it'd be very nice if the default behavior was to generate appropriate Ninja/make targets for all dub configurations matching the target platform. Selecting the configuration(s) to build in the Ninja/make cmdline would then be a hassle-free breeze.

[atilaneves]

I don't know about this; I don't regularly have to build all configurations even in dub packages that have a lot of them. The ROI isn't particularly high.