The build environment is not guaranteed to have /bin/bash, especially on NixOS
or in our CI runner. Use /usr/bin/env to resolve it from PATH.
diff --git a/python/private/stage1_bootstrap_template.sh b/python/private/stage1_bootstrap_template.sh
--- a/python/private/stage1_bootstrap_template.sh
+++ b/python/private/stage1_bootstrap_template.sh
@@ -1,5 +1,5 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e
 
 if [[ -n "${RULES_PYTHON_BOOTSTRAP_VERBOSE:-}" ]]; then