Bug 2152738

Description of problem:

Fedora installing header files inconsistently causing confusion for cross-platform Vulkan developers.

The following confusion was found on Discord.

```
i'm having problems with building a program with vulkan
on windows (in visual studio 2022), cmake fails to find vulkan with find_package(Vulkan REQUIRED), 
even though the Vulkan SDK seems to be properly installed and the VULKAN_SDK environment variable is set to the correct directory

after trying it again on fedora, my cmake file works fine, but the header files from the vulkan-validation-layers-devel package,
such as vk_enum_string_helper.h are in /usr/include/vulkan/vulkan/ instead of in /usr/include/vulkan/ with the other headers, 
so #include <vulkan/vk_enum_string_helper.h> doesn't work
whereas on windows, those headers are all in the same directory (which is C:\VulkanSDK\1.3.231.1\Include\vulkan for me)
i want to make my code portable and idk what to do about this 
```

Currently the fedora packaging is inconsistent with lunarg packaging (Causing confusion on how to build against the SDK).

In our CMake we specify header files being installed to the include/vulkan folder.
https://github.com/KhronosGroup/Vulkan-ValidationLayers/blob/46f343d06003fdbdafa9d5c9d14a11a08006bc1e/layers/CMakeLists.txt#L61

However, the Fedora packaging has this line here:
https://src.fedoraproject.org/rpms/vulkan-validation-layers/blob/a6ebc0c75fb22a469a12c61092fb90b81bb0e20e/f/vulkan-validation-layers.spec#_60

Which results in the `vulkan/vulkan` inconsistency issue. The `LunarG` packages are consistent.

The fix is just a minor adjustment to the cmake configuration:

```
%cmake3 ....
        -DCMAKE_INSTALL_INCLUDEDIR=%{_includedir}/ # Don't specify Vulkan, the code does that already
	
%cmake_build
```