include Makefile.extra

[Reed Lai]

Seniors,

I use both of autoconf and automake to maintain my project.

I cannot include an extra makefile in Makefile.am, because the
automake will error since that extra makefile is created by
configure and not exist when automake is running.

How do I deal with this requirement automatically without
manually add the extra Makefile to Mailfile.in?  Please help!

Thanks
-- 
Reed Lai