message: Fix extra_test_args
diff: # accompanying file Copyright.txt for details.
  #------------------------------------------------------------------------------#
  +if(ADIOS2_HAVE_MPI)
  + set(extra_test_args EXEC_WRAPPER ${MPIEXEC_COMMAND})
  +endif()
  +
  add_executable(TestSstParamFails TestSstParamFails.cpp)
  target_link_libraries(TestSstParamFails adios2 gtest_interface)
  gtest_add_tests(TARGET TestSstParamFails ${extra_test_args})
  @@ -14,5 +18,4 @@ gtest_add_tests(TARGET TestSstWriterFails ${extra_test_args})
  if(ADIOS2_HAVE_MPI)
  target_link_libraries(TestSstParamFails MPI::MPI_C)
  target_link_libraries(TestSstWriterFails MPI::MPI_C)
  - set(extra_test_args EXEC_WRAPPER ${MPIEXEC_COMMAND})
  endif()
  