Don't hardcode bash location

bash may not be installed in /bin, so don't make that assumption.

Change-Id: I04ae786c7558f829ddf9649c127cbba1457dcfd3
diff --git a/contrib/git-exproll.sh b/contrib/git-exproll.sh
index 066c57c..9ad7a85 100644
--- a/contrib/git-exproll.sh
+++ b/contrib/git-exproll.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Copyright (c) 2012, Code Aurora Forum. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
diff --git a/gerrit-server/src/main/resources/com/google/gerrit/server/tools/root/scripts/reposize.sh b/gerrit-server/src/main/resources/com/google/gerrit/server/tools/root/scripts/reposize.sh
index 70b1776..b835e6b 100755
--- a/gerrit-server/src/main/resources/com/google/gerrit/server/tools/root/scripts/reposize.sh
+++ b/gerrit-server/src/main/resources/com/google/gerrit/server/tools/root/scripts/reposize.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Copyright (C) 2014 The Android Open Source Project
 #
diff --git a/tools/plugin_archetype_deploy.sh b/tools/plugin_archetype_deploy.sh
index b5d1a66..4ad8b70 100755
--- a/tools/plugin_archetype_deploy.sh
+++ b/tools/plugin_archetype_deploy.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Copyright (C) 2014 The Android Open Source Project
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/tools/util/query_tester.sh b/tools/util/query_tester.sh
index 25646c2..db1680b 100755
--- a/tools/util/query_tester.sh
+++ b/tools/util/query_tester.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 usage() {
     cat <<EOF