[bug#58887] [PATCH][staging] gnu: vulkan-loader: Add native-search-paths field.

[Kaelyn]

While the original patch description doesn't mention why the 
native-search-paths variables and associated snippet are needed, if they are to 
fix error messages like:


  !! validation layer: libVkLayer_MESA_device_select.so: cannot open shared 
object file: No such file or directory

when running Vulkan programs including vulkaninfo, then this issue can be 
closed. Commit 61a326442442f9b09911d35b3a3a48cf5335d7d7 fixed the remaining 
Vulkan layer manifest files to include the full paths to the shared libraries, 
which resolved the error messages like the one above about not finding the 
shared object files for layers without introducing new environment variables.