Dependency per system does not work

System information

dub version: 1.35.0
OS Platform and distribution: All
compiler version: All

Bug Description

Dub does not allow overriding/merging dependencies by system.

How to reproduce?

"dependencies-osx": {},
"dependencies-windows": {},
"dependencies-linux": {}

Expected Behavior

It should override or merge them. There is a lot of dependencies that doesn't make sense based on system you're using. e.g: Metal is OSX only. DirectX is Windows only. X11 is almost linux only.

dlang / dub

Dependency per system does not work #2752

System information

Bug Description

How to reproduce?

Expected Behavior

Logs