MangoHud is a Vulkan and OpenGL overlay for monitoring FPS,
temperatures, CPU/GPU load and more.

MangoHud may be built with access to Nvidia's NV_Control X
extension. This introduces a dependency on libxnvctrl and
may be included by passing XNVCTRL=enabled.

By default, MangoHud reaches out to the internet to pull
Vulkan-Headers. Since Slackware ships with vulkan-sdk, we
enable system headers by default. To disable this feature
and restore default behavior, pass SYSVULKAN=disabled to
the build script.

This SlackBuild defaults to building mangoapp as well. To
disable this behavior, pass MANGOAPP=false to the build
script. This removes the dependency on glfw3 and
nlohmann_json.
