Use more convenient and UNIX-agnostic shebang
Pure sh scripts should use /bin/sh as it's available on every platform.
When using bash-specific features, use env to find it, as bash can
be installed in different places according the OS.
diff --git a/ci/emscripten-entry.sh b/ci/emscripten-entry.sh
index acaebfe..22ae8b0 100755
--- a/ci/emscripten-entry.sh
+++ b/ci/emscripten-entry.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
# Copyright 2017 The Rust Project Developers. See the COPYRIGHT
# file at the top-level directory of this distribution and at
# http://rust-lang.org/COPYRIGHT.