[Docker-maint] Bug#800479: Tweak build-deps to allow buildd to make progress on arm64 build

[Hilko Bengen]

* Potter, Tim (Converged Cloud):

>> ,----
>> | Build-Depends: [...]
>> |  golang-go (>= 2:1.4.2-2~) | go-compiler,
>> |  gccgo-5 | go-compiler,
>> |  [...]
>> `----
>
> Hi Hilko. Yes, that looks like it will work also. However I would
> rather add the architecture qualifiers now and remove them later
> rather than have a more complicated B-D line that is permanent.

The advantage in my approach is that it need not be changed and can be
used for other architectures that the golang code base may be ported to.

ppc64, ppc64el seem to have a similar problem right now, don't they?

Cheers,
-Hilko