Fix srun segfault caused by invalid memory reads on the env.

Bug 5561.

src/srun/libsrun/srun_job.c

@@ -1300,6 +1300,8 @@ extern void pre_launch_srun_job(srun_job_t *job, bool slurm_started,
 		slurm_step_launch_abort(job->step_ctx);
 		exit(error_exit);
 	}
+
+	env_array_merge(&job->env, (const char **)__environ);
 }
 
 extern void fini_srun(srun_job_t *job, bool got_alloc, uint32_t *global_rc,

src/srun/srun.c

@@ -597,7 +597,7 @@ static void _setup_one_job_env(slurm_opt_t *opt_local, srun_job_t *job,
 	}
 
 	setup_env(env, srun_opt->preserve_env);
-	job->env = environ;
+	env_array_merge(&job->env, (const char **)environ);
 	xfree(env->task_count);
 	xfree(env);
 }