rust: fix dockerfile for building multiple images in parallel (#1699)

When using `docker compose build` or any other way of building docker
images in parallel the way the cache was working with the rust's
Dockerfile made the caches between images overlap and corrupt each
other. We add a `locked` which prevents multiple writers to the same
cache to fix this behaviour.

rust/Dockerfile

@@ -3,8 +3,8 @@ ARG PACKAGE
 WORKDIR /build/
 COPY . ./
 RUN --mount=type=cache,target=./target \
-    --mount=type=cache,target=/usr/local/cargo/registry \
-    --mount=type=cache,target=/usr/local/rustup \
+    --mount=type=cache,target=/usr/local/cargo/registry,sharing=locked \
+    --mount=type=cache,target=/usr/local/rustup,sharing=locked \
     apt update && apt install -y musl-tools && \
     cargo build -p $PACKAGE --release --target x86_64-unknown-linux-musl