ci: cross compile static binaries for x86_64 and aarch64

from https://gitlab.com/famedly/conduit/-/merge_requests/569

Signed-off-by: strawberry <strawberry@puppygock.gay>

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