more build optimization

Dockerfile

@@ -1,40 +1,37 @@
 # Step -1: Grab mold
-FROM debian:bullseye as mold
+FROM lukemathwalker/cargo-chef as rust-base
 RUN apt-get update && apt-get install -y curl
 ARG MOLD_VERSION=1.7.1
+RUN apt-get update && apt-get install -y --no-install-recommends clang
 RUN curl -sSL https://github.com/rui314/mold/releases/download/v${MOLD_VERSION}/mold-${MOLD_VERSION}-x86_64-linux.tar.gz | tar xzv && \
     mv mold-${MOLD_VERSION}-x86_64-linux/bin/mold /mold && \
     rm -rf mold-${MOLD_VERSION}-x86_64-linux
+ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
+ENV RUSTFLAGS="-C link-arg=-fuse-ld=/mold"
 
 # Step 1: Compute a recipe file
-FROM rust as planner
+FROM rust-base as planner
 WORKDIR /app
 RUN cargo install cargo-chef
 COPY . .
 RUN cargo chef prepare --recipe-path recipe.json
 
 # Step 2: Cache project dependencies
-FROM rust as cacher
+FROM rust-base as cacher
 WORKDIR /app
 RUN cargo install cargo-chef
-RUN apt-get update && apt-get install -y --no-install-recommends clang
 COPY --from=mold /mold /mold
 COPY --from=planner /app/recipe.json recipe.json
-ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
-ENV RUSTFLAGS="-C link-arg=-fuse-ld=/mold"
 RUN cargo chef cook --release --recipe-path recipe.json
 
 # Step 3: Build the binary
-FROM rust as builder
+FROM rust-base as builder
 WORKDIR /app
 RUN apt-get update && apt-get install -y --no-install-recommends clang
 COPY . .
 # Copy over the cached dependencies from above
 COPY --from=cacher /app/target target
-COPY --from=mold /mold /mold
 COPY --from=cacher /usr/local/cargo /usr/local/cargo
-ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
-ENV RUSTFLAGS="-C link-arg=-fuse-ld=/mold"
 ARG SERVICE
 RUN cargo build --release --bin ${SERVICE}