The help2man script is pretty useless to us. It requires to run the target
binary to extract help information which is not possible for any of our
cross compiled target binaries.

We're not interested in man pages for -cross/-native tools.

It therefore makes no sense to have this as a core build dependency.

This patch removes the dependeny and replaces it with a script
returning false. This will trigger autotool's missing utility
to use the copy of the man page included with the sources which
is what would already happen when we tried to run cross compiled
binaries anyway.

(From OE-Core rev: 288343e30604b944dc18fd82172febd314d9c520)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>