Fix some shebangs to make the beasties happy

stdlib/archive/tests/invalid_cases.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 INVOCATION_FILE=tmp_archivetest_invocation_file.json
 

stdlib/archive/tests/valid_cases.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 INVOCATION_FILE=tmp_archivetest_invocation_file.json
 

stdlib/git/tests/simple.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 INVOCATION_FILE=$PWD/tmp_gittest_invocation_file.json