Add intermediate container to hide ARGs

ARGs contain secrets to speed up builds

tests/Complement.Dockerfile

@@ -1,10 +1,21 @@
-FROM valkum/docker-rust-ci:latest
+FROM valkum/docker-rust-ci:latest as builder
 WORKDIR /build
 
+ARG RUSTC_WRAPPER
+ARG AWS_ACCESS_KEY_ID
+ARG AWS_SECRET_ACCESS_KEY
+ARG SCCACHE_BUCKET
+ARG SCCACHE_ENDPOINT
+ARG SCCACHE_S3_USE_SSL
+
 COPY . .
 RUN cargo build
 
+FROM valkum/docker-rust-ci:latest
+WORKDIR /build
+COPY --from=builder /build/target/debug/conduit /conduit
+
 ENV SERVER_NAME=localhost
 EXPOSE 14004 8448
 
-CMD sed "s/server_name: your.server.name/server_name: ${SERVER_NAME}/g" Rocket-example.toml Rocket.toml && ./target/debug/conduit
+CMD sed "s/server_name: your.server.name/server_name: ${SERVER_NAME}/g" Rocket-example.toml Rocket.toml && /conduit