Explicitly select /bin/bash as interpreter for scripts that use bashisms

Change-Id: Iacaeeb1dcfa79272e2f660aa6f35e897a211b86d

faketools/dx

-#!/bin/sh
+#!/bin/bash
 #
 # Copyright (c) 2012, Code Aurora Forum. All rights reserved.
 #

treeid.sh

-#!/bin/sh
+#!/bin/bash
 #
 # Attempt to identify the Android tree in use.  On success one or more
 # tree identifiers are output to stdout.