Fix Cycles Metal failing when run in parallel, always run serial

The command buffer fails to execute, the cause is unknown. It does not
appear to be related to the binary archive cache as disabling that does
not prevent the issue.

Pull Request: https://projects.blender.org/blender/blender/pulls/106328

tests/python/CMakeLists.txt

@@ -693,8 +693,9 @@ if(WITH_CYCLES OR WITH_OPENGL_RENDER_TESTS)
         set(_cycles_render_tests bake;${render_tests};osl)
 
         foreach(render_test ${_cycles_render_tests})
+          set(_cycles_test_name "cycles_${render_test}_${_cycles_device_lower}")
           add_python_test(
-            cycles_${render_test}_${_cycles_device_lower}
+            ${_cycles_test_name}
             ${CMAKE_CURRENT_LIST_DIR}/cycles_render_tests.py
             -blender "${TEST_BLENDER_EXE}"
             -testdir "${TEST_SRC_DIR}/render/${render_test}"
@@ -703,6 +704,11 @@ if(WITH_CYCLES OR WITH_OPENGL_RENDER_TESTS)
             -device ${_cycles_device}
             -blacklist ${_cycles_blacklist}
           )
+
+          if(NOT("${_cycles_device_lower}" STREQUAL "cpu"))
+            set_tests_properties(${_cycles_test_name} PROPERTIES RUN_SERIAL TRUE)
+          endif()
+          unset(_cycles_test_name)
         endforeach()
       endforeach()
     endif()