replace shebang '/bin/bash' for '/usr/bin/env bash'

Allows better portability of bash scripting between Linux
distributions.

Change-Id: Ia0ec079581398bcffbf20bb8206860bcec0e6e7a
Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
diff --git a/script/build_bmcov.sh b/script/build_bmcov.sh
index 3923ab8..0ba1d29 100755
--- a/script/build_bmcov.sh
+++ b/script/build_bmcov.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Copyright (c) 2019-2020, Arm Limited. All rights reserved.
 #
@@ -103,7 +103,7 @@
     fi
     # to be run on the user locally
     cat <<EOF > "server.sh"
-#!/bin/bash
+#!/usr/bin/env bash
 
 echo "Running server..."
 type -a firefox || (echo "Please install Firefox..." && exit 1)