Auto merge of #5405 - dwijnand:contributing-lint-overrides, r=matklad

Detail how to override lint warnings when compiling tests

alternative to #5403

Author: bors

ARCHITECTURE.md

@@ -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