message: Tweak to compile with Apple Clang v13.0
  macos-11 Apple Clang does not support -Wno-unused-but-set-variable
  To fix CI
  error: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Werror,-Wunknown-warning-option]
diff: @@ -405,7 +405,11 @@ if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  list(APPEND warning_flags -Wno-unused-lambda-capture)
  endif()
  - if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 13.0)
  + if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 13.0 AND NOT APPLE)
  + list(APPEND warning_flags -Wno-unused-but-set-variable -Wno-deprecated-copy)
  + endif()
  +
  + if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 13.1 AND APPLE)
  list(APPEND warning_flags -Wno-unused-but-set-variable -Wno-deprecated-copy)
  endif()
  