Log Message:
x11/xorg-cf-files: Make empty host.def when cross-compiling.

Otherwise, MAKE_PROGRAM from the build environment gets baked into
the package, which is wrong.

NetBSD does this in xsrc, so it must not matter that much!  In any
case, I think most of this xorg-cf-files business is long since
obsolete in the modular X.org era?