change shebang of shell script to make it work on both of Ubuntu or FreeBSD

cook.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Configuration
 export TARGET=x86_64-unknown-redox

setup.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -e
 
 echo "Downloading latest libc-artifacts"

update-packages.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e