use nix-built binary to produce debian package

Currently just for `x86_64-unknown-linux-musl`. Theoretically, we can
use this same mechanism for `aarch64-unknown-linux-musl`. Practically,
I'm not sure just this will even work.

.gitlab-ci.yml

@@ -43,13 +43,18 @@ ci:
       - target
       - .gitlab-ci.d
 
-nix:artifacts:
+artifacts:
   stage: artifacts
   image: nixos/nix:2.20.4
   script:
     - ./bin/nix-build-and-cache .#static-x86_64-unknown-linux-musl
     - cp result/bin/conduit x86_64-unknown-linux-musl
 
+    - mkdir -p target/release
+    - cp result/bin/conduit target/release
+    - direnv exec . cargo deb --no-build
+    - mv target/debian/*.deb x86_64-unknown-linux-musl.deb
+
     # Since the OCI image package is based on the binary package, this has the
     # fun side effect of uploading the normal binary too. Conduit users who are
     # deploying with Nix can leverage this fact by adding our binary cache to
@@ -70,29 +75,10 @@ nix:artifacts:
     paths:
       - x86_64-unknown-linux-musl
       - aarch64-unknown-linux-musl
+      - x86_64-unknown-linux-musl.deb
       - oci-image-amd64.tar.gz
       - oci-image-arm64v8.tar.gz
 
-debian:x86_64-unknown-linux-gnu:
-  stage: artifacts
-  # See also `rust-toolchain.toml`
-  image: rust:1.75.0
-  script:
-    - apt-get update && apt-get install -y --no-install-recommends libclang-dev
-    - cargo install cargo-deb
-    - cargo deb
-
-    # Make the output less difficult to find
-    - mv target/debian/*.deb conduit.deb
-  artifacts:
-    paths:
-      - conduit.deb
-  cache:
-    key: debian
-    paths:
-      - target
-      - .gitlab-ci.d
-
 .push-oci-image:
   stage: publish
   image: docker:25.0.0
@@ -124,7 +110,7 @@ debian:x86_64-unknown-linux-gnu:
         docker manifest push $IMAGE_NAME:latest
       fi
   dependencies:
-    - nix:artifacts
+    - artifacts
   only:
     - next
     - master