message: add required cc flag for build
diff: @@ -84,6 +84,7 @@ fn build_wrapper(opencv: pkg_config::Library) -> Result<(), Box<dyn Error>> {
  let mut gcc = cc::Build::new();
  gcc.cpp(true)
  + .flag("-std=c++11")
  .flag_if_supported("-Wno-deprecated-declarations")
  .flag_if_supported("-Wno-class-memaccess")
  ;
  