Do not assume that bash is installed in /bin (#477)

This is required in order to run the tests on *BSD.

configure

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 echo "Use Bazel, CMake or Premake5 to generate projects / build files."
 echo "  Bazel: http://www.bazel.build/"
 echo "  CMake: https://cmake.org/"

fuzz/test_fuzzer.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 BROTLI="$( cd "$( dirname "${BASH_SOURCE[0]}" )/.." && pwd )"
 

tests/compatibility_test.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Test that the brotli command-line tool can decompress old brotli-compressed
 # files.

tests/roundtrip_test.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Roundtrip test for the brotli command-line tool.