Update CMake to use gameinput package (#498)

CMakeLists.txt

@@ -292,10 +292,15 @@ include(CheckIncludeFileCXX)
 
 if(BUILD_GAMEINPUT)
     message(STATUS "Using GameInput for GamePad/Keyboard/Mouse.")
-    set(CMAKE_REQUIRED_QUIET ON)
-    CHECK_INCLUDE_FILE_CXX(GameInput.h GAMEINPUT_HEADER)
-    if(NOT GAMEINPUT_HEADER)
-        message(FATAL_ERROR "Microsoft GDK required to build GameInput. See https://aka.ms/gdk")
+    find_package(gameinput CONFIG QUIET)
+    if(gameinput_FOUND)
+      target_link_libraries(${PROJECT_NAME} PUBLIC Microsoft::GameInput)
+    else()
+      set(CMAKE_REQUIRED_QUIET ON)
+      CHECK_INCLUDE_FILE_CXX(GameInput.h GAMEINPUT_HEADER)
+      if(NOT GAMEINPUT_HEADER)
+          message(FATAL_ERROR "Microsoft GDK required to build GameInput. See https://aka.ms/gdk")
+      endif()
     endif()
     target_compile_definitions(${PROJECT_NAME} PUBLIC USING_GAMEINPUT)
 elseif(BUILD_WGI)