The vkd3d folder is a submodule linked to https://github.com/ValveSoftware/vkd3d. However, this repository doesn't exist. Also, the commit that the submodule points to doesn't exist upstream. This means that it's impossible to build Proton-4.11-8 as provided.
The vkd3d folder is a submodule linked to https://github.com/ValveSoftware/vkd3d. However, this repository doesn't exist. Also, the commit that the submodule points to doesn't exist upstream. This means that it's impossible to build Proton-4.11-8 as provided.