fix(script): enforce gawk to be installed

If gawk is not installed, a weird error is encountered as shown
below when make_stress_test_image.sh script is executed locally:

losetup: failed to parse size: '5.24078e+09': Invalid argument

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Ibe3b212516e2cc036f1503f61786c146ea885b78
diff --git a/script/make_stress_test_image.sh b/script/make_stress_test_image.sh
index 3ea3344..f10f7df 100755
--- a/script/make_stress_test_image.sh
+++ b/script/make_stress_test_image.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 #
-# Copyright (c) 2019-2020 Arm Limited. All rights reserved.
+# Copyright (c) 2019-2022 Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -15,6 +15,12 @@
 
 set -e
 
+if ! [ -x "$(command -v gawk)" ]; then
+	echo "Error: gawk is not installed."
+	echo "Run 'apt-get install gawk' to install"
+	exit 1
+fi
+
 extract_script() {
 	local to="${name:?}.sh"