Fix Rust toolchain environment issue on RustRover (#1497)

* Fix Rust toolchain environment issue on RustRover

* Disable auto rustup update

Tool: gitpod/catfood.gitpod.cloud

chunks/lang-rust/Dockerfile

@@ -14,9 +14,11 @@ ENV PATH=$HOME/.cargo/bin:$PATH
 RUN curl -fsSL https://sh.rustup.rs | sh -s -- -y --no-modify-path --default-toolchain ${RUST_VERSION} \
         -c rls rust-analysis rust-src rustfmt clippy \
     && for cmp in rustup cargo; do rustup completions bash "$cmp" > "$HOME/.local/share/bash-completion/completions/$cmp"; done \
-    && printf '%s\n'    'export CARGO_HOME=/workspace/.cargo' \
-                        'mkdir -m 0755 -p "$CARGO_HOME/bin" 2>/dev/null' \
-                        'export PATH=$CARGO_HOME/bin:$PATH' \
-                        'test ! -e "$CARGO_HOME/bin/rustup" && mv "$(command -v rustup)" "$CARGO_HOME/bin"' > $HOME/.bashrc.d/80-rust \
     && cargo install cargo-watch cargo-edit cargo-workspaces \
     && rm -rf "$HOME/.cargo/registry" # This registry cache is now useless as we change the CARGO_HOME path to `/workspace`
+
+# Helpful for Gitpod prebuilds
+RUN rustup set auto-self-update disable
+ENV CARGO_HOME=/workspace/.cargo
+ENV CARGO_INSTALL_ROOT=$HOME/.cargo
+ENV RUSTUP_HOME=$HOME/.rustup