gdb source and binary for experimental?

[Svante Signell <srs@kth.se>]

Hi,

I was asked to check if the HEAD of gdb in experimental works for Debian
Hurd without the prune threads patch. When tying to install it, I found
that it is not yet built due to a build dependency on autoconf-2.68-1,
which is now available. However, it is not yet on the buildds. Note that
due to the -Wall -Werror flags, -Werror has to be disabled for
gdb/msg_U.c. (-Wstrict-aliasing).

Furthermore, when adding 

deb-src http://ftp.se.debian.org/debian/ experimental

I expected to be able to download the source package by

apt-get source -t experimental gdb or
apt-get source gdb/experimental

Instead I get the error:
> > E: Ignore unavailable target release 'experimental' of package 'gdb'
> > E: Unable to find a source package for

This works in Linux, what is wrong in Hurd?