Include note about bug while building on macOS in mdbook

Author: russweas

src/doc/contrib/src/process/working-on-cargo.md

@@ -46,6 +46,11 @@ If you can successfully run `cargo build`, you should be good to go!
 
 [homebrew]: https://brew.sh/
 
+Note: There is currently a bug on macOS that will cause an error while linking 
+cargo. To fix this, run `export MACOSX_DEPLOYMENT_TARGET=10.7` before attempting
+to build the cargo project. For more information, see 
+[rust#90342](https://github.com/rust-lang/rust/issues/90342).
+
 ## Running Cargo
 
 You can use `cargo run` to run cargo itself, or you can use the path directly