docker: Refactor feat_set out of base layers.

Signed-off-by: Jason Volk <jason@zemos.net>

docker/Dockerfile.rust

@@ -0,0 +1,71 @@
+# syntax = docker/dockerfile:1.11-labs
+
+FROM input AS rustup
+ARG RUST_HOME
+ARG rust_target
+ARG rustup_version="1.28.1"
+ARG rustup_profile="minimal"
+
+WORKDIR /
+COPY --link --from=input . .
+
+WORKDIR ${RUST_HOME}
+RUN <<EOF
+    set -eux
+
+    url="https://static.rust-lang.org/rustup/archive/${rustup_version}/${rust_target}/rustup-init"
+    curl -S -O -s "$url"
+    chmod o+x rustup-init
+EOF
+
+FROM input AS rust
+ARG rust_toolchain
+ARG rust_target
+ARG RUST_HOME
+ARG RUSTUP_HOME
+ARG CARGO_HOME
+ARG CARGO_TARGET
+ARG rustup_version="1.28.1"
+ARG rustup_profile="minimal"
+ARG CARGO_TERM_VERBOSE
+ARG rustup_components
+ARG cargo_installs
+
+WORKDIR /
+COPY --link --from=input . .
+
+WORKDIR ${RUST_HOME}
+ENV CARGO_TARGET="${rust_target}"
+ENV RUSTUP_HOME="${RUSTUP_HOME}"
+ENV CARGO_HOME="${CARGO_HOME}"
+ENV PATH="${CARGO_HOME}/bin:$PATH"
+RUN \
+--mount=type=cache,dst=${RUSTUP_HOME}/downloads,sharing=locked \
+--mount=type=cache,dst=${CARGO_HOME}/registry,sharing=locked \
+--mount=type=cache,dst=${CARGO_HOME}/git,sharing=locked \
+<<EOF
+    set -eux
+    ./rustup-init -y \
+        --quiet \
+        --profile "${rustup_profile}" \
+        --default-host "${CARGO_TARGET}" \
+        --default-toolchain "${rust_toolchain}" \
+        --no-update-default-toolchain \
+        --no-modify-path
+
+    chmod -R go+rw $CARGO_HOME $RUSTUP_HOME
+    rm rustup-init
+
+    rustup component add \
+        --toolchain ${rust_toolchain} \
+        --target ${rust_target} \
+        ${rustup_components} \
+        ;
+
+    rustup run --install ${rust_toolchain} \
+        cargo install \
+            --locked \
+            --target ${rust_target} \
+            ${cargo_installs} \
+            ;
+EOF