message: Detail how to override lint warnings when compiling tests
diff: @@ -106,6 +106,10 @@ assert_that(
  Alternatively to build and run a custom version of cargo simply run `cargo build`
  and execute `target/debug/cargo`.
  +Because the test suite has `#![deny(warnings)]` at times you might find it
  +convenient to override this with `RUSTFLAGS`, for example
  +`RUSTFLAGS="--cap-lints warn" cargo build`.
  +
  ## Logging
  Cargo uses [`env_logger`](https://docs.rs/env_logger/*/env_logger/), so you can set
  