Vulkan Loader doesn't return an error when the driver binary couldn't be found

[christophe-lunarg]

Describe the bug
After discussions with @richard-lunarg and @aitor-lunarg, I started investigating running Lavapipe and KosmicKrisp on macOS using vk_loader_settings.json (generated from Vulkan Configurator).

When adding drivers, eg the following vk_loader_settings.json file, the additional drivers are not found by Vulkan Configurator or vulkaninfo.

Additionally, simply copying the additional drivers in /usr/local/share/vulkan/icd.d next to MoltenVK doesn't work either.

Environment (please complete the following information):

• OS: macOS

To Reproduce

[vk_loader_settings.json](https://github.com/user-attachments/files/23125923/vk_loader_settings.json)

vulkaninfo --summary:
log.txt

Additional context

[christophe-lunarg]

Actually, I believe it was (mostly) a user error!
The binary needs to be located where the manifest says it is.

A problem is that the Vulkan Loader ignore these file without reporting and error in the log when the binary could not be found.