util: Update all shebangs to use /usr/bin/env

Instead of hardcoding paths to the executables, use the version in the
path.  This allows the scripts to work on more systems, and allows the
binary version to be changed more easily if needed.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: Ifcc56aa21092cd3866eacb6a02d198110ec6051d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48904
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

util/gitconfig/test/commit-message-hook.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 ##
 ## This program is free software; you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by