Fix failing Travis report generation

Signed-off-by: Salome Thirot <salome.thirot@arm.com>

Author: salomethirot-arm

ci/fih_test_docker/fi_tester_gdb.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (c) 2020 Arm Limited
+# Copyright (c) 2021 Arm Limited
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -104,7 +104,7 @@ EOF
                 echo "    test_exec_ok: True"
                 echo "    skipped: True"
                 echo "    boot: False"
-                echo "    last_line: '$LAST_LINE' "
+                echo "    last_line: \"$LAST_LINE\" "
             fi
         else
             # The target was not stopped at the desired address.