userland: native testing

run

@@ -39,8 +39,13 @@ Ctrl +C kills the QEMU simulator instead of being passed to the guest.
 '''
         )
         self.add_argument(
-            '-D', '--debug-vm', default=False,
-            help='Run GDB on the emulator itself.'
+            '-D',
+            '--debug-vm',
+            default=False,
+            help='''\
+Run GDB on the emulator itself.
+For --emulator native, this debugs the target program.
+'''
         )
         self.add_argument(
             '--debug-vm-args', default='',
@@ -669,7 +674,7 @@ Extra options to append at the end of the emulator command line.
             ])
         cmd.extend(extra_emulator_args)
         cmd.extend(self.env['extra_emulator_args'])
-        if self.env['emulator'] == 'qemu' and self.env['userland']:
+        if self.env['userland'] and self.env['emulator'] in ('qemu', 'native'):
             # The program and arguments must come at the every end of the CLI.
             cmd.extend([self.resolve_userland_executable(self.env['userland']), LF])
             if self.env['userland_args'] is not None: