debug/gdb: fix building the native tic

The native 'tic' will _always_ be run on the build
machine, so no need to handle canadian/native/...

Reported by: Trevor Woerner
http://sourceware.org/ml/crossgcc/2010-03/msg00055.html
(transplanted from 26e89d367ea11660fd3a0bf0bcad8763e4fa21cf)

 # m68k specific configuration file

 # depends on EXPERIMENTAL

 config ARCH_m68k

     select ARCH_SUPPORTS_32

     select ARCH_DEFAULT_32

     select ARCH_DEFAULT_BE

     select ARCH_SUPPORT_CPU

      help

       The m68k architecture