message: build_system: ignore unknown warning option
diff: @@ -30,6 +30,9 @@ else()
  if (WERROR)
  set(warnings "${warnings} -Werror")
  endif()
  +
  + # Allow #pragma GCC diagnostic ignored "-Wstringop-truncation"
  + set(warnings "${warnings} -Wno-pragmas -Wno-unknown-warning-option")
  endif()
  