push oci image and x86_64-*-gnu build to bin cache

This will allow most Nix users to use the `default` package and without
having to build from source. And also allows any weirdos to get the OCI
image from the Nix binary cache if they want. No idea why that would be
desireable though lol

.gitlab-ci.yml

@@ -46,7 +46,13 @@ oci-image:x86_64-unknown-linux-gnu:
   stage: artifacts
   image: nixos/nix:2.19.2
   script:
-    - nix build .#oci-image
+    # Push artifacts and build requirements to binary cache
+    #
+    # 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
+    # their systems.
+    - ./bin/nix-build-and-cache .#oci-image
 
     # Make the output less difficult to find
     - cp result oci-image.tar.gz

bin/nix-build-and-cache

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# The first argument must be the desired installable
+INSTALLABLE="$1"
+
+# Build the installable and forward any other arguments too
+nix build "$@"
+
+if [ ! -z ${ATTIC_TOKEN+x} ]; then
+
+nix run --inputs-from . attic -- login \
+    conduit \
+        https://nix.computer.surgery/conduit \
+        "$ATTIC_TOKEN"
+
+    push_args=(
+        # Attic and its build dependencies
+        "$(nix path-info --inputs-from . attic)"
+        "$(nix path-info --inputs-from . attic --derivation)"
+
+        # The target installable and its build dependencies
+        "$(nix path-info "$INSTALLABLE" --derivation)"
+        "$(nix path-info "$INSTALLABLE")"
+    )
+
+    nix run --inputs-from . attic -- push conduit "${push_args[@]}"
+else
+    echo "\$ATTIC_TOKEN is unset, skipping uploading to the binary cache"
+fi