test: don't run testautomation in parallel

test/CMakeLists.txt

@@ -624,10 +624,11 @@ foreach(TARGET ${SDL_TEST_EXECUTABLES})
 endforeach()
 
 add_sdl_test(testautomation-no-simd testautomation)
-set_property(TEST testautomation-no-simd APPEND PROPERTY ENVIRONMENT "SDL_CPU_FEATURE_MASK=-all")
-
 add_sdl_test(testplatform-no-simd testplatform)
-set_property(TEST testplatform-no-simd APPEND PROPERTY ENVIRONMENT "SDL_CPU_FEATURE_MASK=-all")
+set_property(TEST testautomation-no-simd testplatform-no-simd APPEND PROPERTY ENVIRONMENT "SDL_CPU_FEATURE_MASK=-all")
+
+# testautomation creates temporary files which might conflict
+set_property(TEST testautomation-no-simd testautomation PROPERTY RUN_SERIAL TRUE)
 
 if(SDL_INSTALL_TESTS)
     if(RISCOS)