fix: get nix on PATH

Author: samrose

.github/workflows/nix-build.yml

@@ -68,6 +68,7 @@ jobs:
           curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install --no-confirm \
           --extra-conf "substituters = https://cache.nixos.org https://nix-postgres-artifacts.s3.amazonaws.com" \
           --extra-conf "trusted-public-keys = nix-postgres-artifacts:dGZlQOvKcNEjvT7QEAJbcV6b6uk7VF/hWMjhYleiaLI=% cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+          . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh
           cp ./docker/nix/build_nix.sh ./build_nix.sh
           sed -i '' 's/cd workspace//g' ./build_nix.sh
           sed -i '' '1s|^#!/bin/env bash|#!/usr/bin/env bash|' ./build_nix.sh