Add TestSDL2 only for emscripten platform

- closes #19612

Rendering/OpenGL2/Testing/Cxx/CMakeLists.txt

@@ -112,8 +112,10 @@ endif()
 set_tests_properties(VTK::RenderingOpenGL2Cxx-TestFramebufferHDR
   PROPERTIES TIMEOUT ${VTK_TEST_TIMEOUT_TestFramebufferHDR})
 
-if (VTK_USE_SDL2)
-  vtk_add_test_cxx(vtkRenderingOpenGL2CxxTests tests TestSDL2.cxx)
+if (CMAKE_SYSTEM_NAME STREQUAL "Emscripten")
+  if (VTK_USE_SDL2)
+    vtk_add_test_cxx(vtkRenderingOpenGL2CxxTests tests TestSDL2.cxx)
+  endif ()
 endif ()
 
 if (NOT VTK_OPENGL_USE_GLES)