playground/test.sh: update test.sh script to use new shell_test::build_go_binary function and work dir setup.
playground/test.sh: update test.sh script to use new shell_test::build_go_binary function and work dir setup.

Change-Id: I76ca49ff1f38df86ffd153ee23aa949d6a8090f9

vanadium/playground,vanadium/playground,vanadium/playground,vanadium/playground