message: Add cfg settings for enabled modules...
  ...so that you can conditionally compile with, say, #[cfg(mod_dnn)].
diff: @@ -699,6 +699,10 @@ fn make_modules(opencv_dir_as_string: &str) -> Result<()> {
  })
  .collect();
  + for m in &modules {
  + println!("cargo:rustc-cfg=mod_{}", m);
  + }
  +
  MODULES.set(modules).expect("Can't set MODULES cache");
  Ok(())
  }
  