Dropping gdc support?

[Samuel Thibault]

Hello,

The gcc-12 package fails to build because it notices that gdc-11 does
not work. Actually gdc has never worked as far as I can still test. And
indeed the packages that were build-depending on it are failing.
Basically it cannot work because the D runtime has not been ported
to the Hurd system. It seems that it's like all these new languages
implementations: one has to write by hand in D each and every bit of the
Posix ABI (while perl has been doing such thing automatically from C
headers for decades). If somebody volunteers to do the porting that will
be welcome, otherwise I'll soon ask to just drop the gdc support from
gcc-12, only a dozen or two Debian packages will miss that.

Samuel