helper/options: handle errors in -l

Before the patch an error in opening the log file (e.g. can't write a
file) was ignored when specified via `-l`.
E.g.:
```
> touch log
> chmod -w log
> openocd -l log -c shutdown
...
failed to open output log "log"
shutdown command invoked
> echo $?
0
```

After the patch:
```
...
> openocd -l log -c shutdown
...
failed to open output log "log"
> echo $?
1
```

Change-Id: Ibab45f580dc46a499bf967c4afad071f9c2972a2
Signed-off-by: Evgeniy Naydanov <[email protected]>
Reviewed-on: https://review.openocd.org/c/openocd/+/8666
Tested-by: jenkins
Reviewed-by: Antonio Borneo <[email protected]>

Author: en-sc

src/helper/options.c

@@ -303,8 +303,12 @@ int parse_cmdline_args(struct command_context *cmd_ctx, int argc, char *argv[])
 				break;
 			}
 			case 'l':		/* --log_output | -l */
-				command_run_linef(cmd_ctx, "log_output %s", optarg);
+			{
+				int retval = command_run_linef(cmd_ctx, "log_output %s", optarg);
+				if (retval != ERROR_OK)
+					return retval;
 				break;
+			}
 			case 'c':		/* --command | -c */
 				add_config_command(optarg);
 				break;