Auto merge of #376 - kamalmarhubi:warnings-in-test, r=utkarshkukreti
Auto merge of #376 - kamalmarhubi:warnings-in-test, r=utkarshkukreti

Only deny warnings in test

This prevents us breaking builds under newer Rust versions with
additional warnings.

Susurrus/nix,asomers/nix,posborne/rust-nix,nix-rust/nix,nix-rust/nix,Susurrus/nix,asomers/nix,carllerche/nix-rust,geofft/nix-rust,xd009642/nix,berkowski/nix,geofft/nix-rust,posborne/rust-nix,MarkusJais/nix-rust,kamalmarhubi/nix-rust,kamalmarhubi/nix-rust,xd009642/nix,xd009642/nix,kamalmarhubi/nix-rust,carllerche/nix-rust,MarkusJais/nix-rust,MarkusJais/nix-rust,carllerche/nix-rust,geofft/nix-rust,berkowski/nix,Susurrus/nix,berkowski/nix,posborne/rust-nix