Full configuration of SDL_INSTALL_CMAKEDIR_ROOT

Let users override also the final `SDL3` subdir for the configuration installation destination.

CMakeLists.txt

@@ -3437,7 +3437,7 @@ endif()
 if(WINDOWS AND NOT MINGW)
   set(SDL_INSTALL_CMAKEDIR_ROOT_DEFAULT "cmake")
 else()
-  set(SDL_INSTALL_CMAKEDIR_ROOT_DEFAULT "${CMAKE_INSTALL_LIBDIR}/cmake")
+  set(SDL_INSTALL_CMAKEDIR_ROOT_DEFAULT "${CMAKE_INSTALL_LIBDIR}/cmake/SDL3")
 endif()
 set(SDL_INSTALL_CMAKEDIR_ROOT "${SDL_INSTALL_CMAKEDIR_ROOT_DEFAULT}" CACHE STRING "Root folder where to install SDL3Config.cmake related files (SDL3 subfolder for MSVC projects)")
 
@@ -3457,7 +3457,7 @@ elseif(SDL_FRAMEWORK)
   set(SDL_INSTALL_LICENSEDIR "Resources")
   set(SDL_INSTALL_HEADERSDIR "Headers")
 else()
-  set(SDL_INSTALL_CMAKEDIR "${SDL_INSTALL_CMAKEDIR_ROOT}/SDL3")
+  set(SDL_INSTALL_CMAKEDIR "${SDL_INSTALL_CMAKEDIR_ROOT}")
   set(SDL_INSTALL_LICENSEDIR "${CMAKE_INSTALL_DATAROOTDIR}/licenses/${PROJECT_NAME}")
   set(SDL_INSTALL_HEADERSDIR "${CMAKE_INSTALL_INCLUDEDIR}/SDL3")
 endif()