cmake: Removed unused SDL_GPU_DXVK bits.

Reference Issue #13938.

CMakeLists.txt

@@ -382,7 +382,6 @@ set_option(SDL_LIBUDEV             "Enable libudev support" ON)
 set_option(SDL_ASAN                "Use AddressSanitizer to detect memory errors" OFF)
 set_option(SDL_CCACHE              "Use Ccache to speed up build" OFF)
 set_option(SDL_CLANG_TIDY          "Run clang-tidy static analysis" OFF)
-set_option(SDL_GPU_DXVK            "Build SDL_GPU with DXVK support" OFF)
 
 set(SDL_VENDOR_INFO "" CACHE STRING "Vendor name and/or version to add to SDL_REVISION")
 
@@ -1989,16 +1988,6 @@ elseif(UNIX AND NOT APPLE AND NOT RISCOS AND NOT HAIKU)
       )
     endif()
 
-    if(SDL_GPU AND SDL_GPU_DXVK)
-      if(PKG_CONFIG_FOUND)
-        pkg_search_module(DXVK_NATIVE dxvk-dxgi)
-        if(DXVK_NATIVE_FOUND)
-          set(HAVE_D3D11_H TRUE)
-          sdl_include_directories(PRIVATE SYSTEM ${DXVK_NATIVE_INCLUDE_DIRS})
-        endif()
-      endif()
-    endif()
-
     if(HAVE_LIBURING_H)
       sdl_sources("${SDL3_SOURCE_DIR}/src/io/io_uring/SDL_asyncio_liburing.c")
     endif()