Bug 1645829 - mozlint: Show the version of rustc r=linter-reviewers,ahal

Also, make a change to force the installation of a more recent version
of clippy & rustfmt until we have a proper fix

Differential Revision: https://phabricator.services.mozilla.com/D79735

taskcluster/docker/lint/system-setup.sh

@@ -119,6 +119,7 @@ mkdir -p "$CARGO_HOME"
 curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
 "$RUSTUP_HOME"/bin/rustup component add rustfmt
 "$RUSTUP_HOME"/bin/rustup component add clippy
+"$RUSTUP_HOME"/bin/rustc --version
 "$RUSTUP_HOME"/bin/rustfmt --version
 "$CARGO_HOME"/bin/cargo clippy --version