Nightly images are not __identical__ to official images, as claimed

[mdharm]

The description for the nightly images (i.e. rustlang/rust:nightly) from Docker Hub says:

This image has two tags, nightly and nightly-slim, which are updated every day to match the current Rust nightly. The nightly tag is configured identically to that of the latest tag of the official image, except that the nightly toolchain is selected via rustup. The nightly-slim tag is configured identically to that of the slim tag of the official image, except that the nightly toolchain is selected via rustup.

However, this is not correct. The official images are created using --profile minimal (which significantly reduces the image size). The --default-host is also set, but this has little practical difference as only one toolchain is installed.

The nightly images should either use --profile minimal to match the official builds, or the description text should be updated to indicate this difference.