Auto merge of #7755 - lu-zero:rustc-crate-type, r=alexcrichton
Auto merge of #7755 - lu-zero:rustc-crate-type, r=alexcrichton

Make cargo-rustc crate-type-aware

This fixes #7339 and makes the usage of `cargo rustc` less surprising overall.

nipunn1313/cargo,vojtechkral/cargo,rustyhorde/cargo,tshepang/cargo,rust-lang/cargo,nipunn1313/cargo,eminence/cargo,tsurai/cargo,tsurai/cargo,tshepang/cargo,tshepang/cargo,nipunn1313/cargo,rust-lang/cargo,rustyhorde/cargo,eminence/cargo,rustyhorde/cargo,tsurai/cargo,tsurai/cargo,vojtechkral/cargo,nipunn1313/cargo,eminence/cargo,tshepang/cargo,rustyhorde/cargo,vojtechkral/cargo,eminence/cargo,rust-lang/cargo,tsurai/cargo,rust-lang/cargo,vojtechkral/cargo