imagetest-qemu: Add test case for dmesg check in target

Add a test case for error log check with command dmesg in target. The
case introduces a new folder in target, "/opt/test", which holds test
scripts running in target.

Signed-off-by Jiajun Xu <jiajun.xu@intel.com>

scripts/qemuimage-tests/tools/dmesg.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+# Dmesg test script running in QEMU
+#
+# Author: Jiajun Xu <jiajun.xu@intel.com>
+#
+# This file is licensed under the GNU General Public License,
+# Version 2.
+#
+
+which dmesg
+if [ $? -ne 0 ]; then
+	echo "QEMU: No dmesg command found"
+	exit 1
+fi
+
+dmesg | grep -iq "error"
+if [ $? -eq 0 ]; then
+	echo "QEMU: There is some error log in dmesg:"
+	echo "QEMU: ##### Error Log ######"
+	dmesg | grep -i "error"
+	echo "QEMU: #####    End     ######"
+	exit 1
+else
+	echo "QEMU: No error log in dmesg"
+	exit 0
+fi