should interpret relative paths the same way Vulkan does

Created by: smcv

On #187 (closed) I asked

If the library_path is a relative path containing /, for example ../libEGL_myvendor.so, what is it relative to? At the moment it gets passed directly to dlopen(), so the answer is the current working directory of the process that loaded libEGL, which I suspect is not what anyone wants. The Vulkan loader interprets relative paths as relative to the JSON file, which I think is probably more useful

Would you accept a patch to make it consistent with the reference Vulkan loader?

and @kbrenneman replied

Sure. Keeping EGL a little more consistent with Vulkan is probably worthwhile, and I certainly can't think of any use for the current behavior for a relative path.

I'll try to do a MR for this at some point.