cmake: fix SDL_RENDER_VULKAN reporting

Also fix an error when configuring with `-DSDL_VULKAN=ON
-DSDL_RENDER_VULKAN=FALSE`: the vulkan renderer is now correctly
disabled.

CMakeLists.txt

@@ -2010,6 +2010,7 @@ elseif(WINDOWS)
       set(HAVE_VULKAN TRUE)
       if(SDL_RENDER_VULKAN)
         set(SDL_VIDEO_RENDER_VULKAN 1)
+        set(HAVE_RENDER_VULKAN TRUE)
       endif()
     endif()
   endif()
@@ -2254,6 +2255,7 @@ elseif(APPLE)
           set(HAVE_VULKAN TRUE)
           if(SDL_RENDER_VULKAN)
             set(SDL_VIDEO_RENDER_VULKAN 1)
+            set(HAVE_RENDER_VULKAN TRUE)
           endif()
         endif()
         if(SDL_METAL)

cmake/sdlchecks.cmake

@@ -725,7 +725,10 @@ macro(CheckVulkan)
   if(SDL_VULKAN)
     set(SDL_VIDEO_VULKAN 1)
     set(HAVE_VULKAN TRUE)
-    set(SDL_VIDEO_RENDER_VULKAN 1)
+    if(SDL_RENDER_VULKAN)
+      set(SDL_VIDEO_RENDER_VULKAN 1)
+      set(HAVE_RENDER_VULKAN TRUE)
+    endif()
   endif()
 endmacro()