add rust to path and flatten image to single layer

Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:noble-20240114
+FROM ubuntu:noble-20240114 AS base
 
 RUN apt-get update && \
     apt-get install -y \
@@ -8,4 +8,8 @@ RUN apt-get update && \
 
 RUN curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly -y
 
+ENV PATH="/root/.cargo/bin:${PATH}"
+
 WORKDIR /ci
+
+FROM base