Fix the following -Werror warning from clang 10.0.0 in sconfig:

sbin/sconfig/sconfig.c:909:5: error: misleading indentation; statement is not part of the previous 'else' [-Werror,-Wmisleading-indentation]

exit (-1);
^

sbin/sconfig/sconfig.c:907:6: note: previous statement is here

} else
  ^

The intent was to group the exit() call with the previous fprintf()
call.

MFC after: 3 days