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

[Hilko Bengen]

* Potter, Tim (Converged Cloud):

> diff --git a/debian/control b/debian/control
> index 3c4c8c2..0dfb677 100644
> --- a/debian/control
> +++ b/debian/control
> @@ -10,7 +10,7 @@ Vcs-Git: git://anonscm.debian.org/pkg-golang/golang.git
>  Build-Depends: bison,
>                 debhelper (>= 7.4.10),
>                 ed,
> -               golang-go (>= 2:1.4.2-2~) | gccgo-5,
> +               golang-go (>= 2:1.4.2-2~) [!arm64] | gccgo-5 [arm64],
>                 mawk | awk,
>                 netbase,
>                 perl

One would have to revert this once the package has been successfully
built on arm64. Would something like this work?

,----
| Build-Depends: [...]
|  golang-go (>= 2:1.4.2-2~) | go-compiler,
|  gccgo-5 | go-compiler,
|  [...]
`----

Cheers,
-Hilko