ci, nix: build and cache all packages and CI dependencies

from f5bd9bc45e
with changes for GitHub CI and misc

Co-authored-by: Charles Hall <charles@computer.surgery>
Signed-off-by: strawberry <strawberry@puppygock.gay>

bin/complement

@@ -17,7 +17,9 @@ RESULTS_FILE="$3"
 
 OCI_IMAGE="complement-conduit:dev"
 
-pushd "$(git rev-parse --show-toplevel)" > /dev/null
+toplevel="$(git rev-parse --show-toplevel)"
+
+pushd "$toplevel" > /dev/null
 # uses nix-output-monitor (nom) if available
 if command -v nom &> /dev/null; then
     nom build .#complement