try fix script

lib.nix

@@ -1,7 +1,7 @@
 { pkgs }:
 let
   inherit (pkgs) lib;
-  runtime = ".compose";
+  runtime = "$(realpath .compose)";
 in
 {
   mkWrapper =
@@ -142,7 +142,9 @@ in
         name = "run-postgres";
         text = ''
           set -euo pipefail
-          export PGDATA=$(realpath ${data_dir}) PGHOST=$(realpath ${runtimeDir}) PGPORT=${builtins.toString port}
+          export PGDATA=${data_dir}
+          export PGHOST=${runtimeDir}
+          export PGPORT=${builtins.toString port}
           mkdir -p ${lib.escapeShellArg runtimeDir}
           ${setupScript}/bin/setup-postgres
           ${package}/bin/postgres