cmake: haiku uses CXX code, so enable it in C-only project

cmake/SDL3Config.cmake.in

@@ -15,7 +15,7 @@ if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/SDL3Targets.cmake")
   set(SDL3_SDL3_FOUND TRUE)
 endif()
 if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/SDL3staticTargets.cmake")
-  if(ANDROID)
+  if(ANDROID OR HAIKU)
     enable_language(CXX)
   endif()
   include("${CMAKE_CURRENT_LIST_DIR}/SDL3staticTargets.cmake")