Using /usr/bin/env bash instead of /bin/bash (#307)

/bin/bash" makes the script Linux-specific, so change it to "/usr/bin/env bash"

scripts/unix_debug_build.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 CLEAN_BUILD=0;
 MAKE_ARGS="";