Bug#971739: release.debian.org: britney thinks ghostscript B-D on libz-dev:native is unsatisfiable

[Simon McVittie <smcv@debian.org>]

Package: release.debian.org
Severity: normal
User: release.debian.org@packages.debian.org
Usertags: britney

The excuses on <https://tracker.debian.org/pkg/ghostscript> say:
* ghostscript unsatisfiable Build-Depends(-Arch) on amd64: libz-dev:native
* ghostscript unsatisfiable Build-Depends(-Arch) on arm64: libz-dev:native
(etc.)

(ghostscript's migration is also blocked by FTBFS #971678, but that isn't
the significant thing here.)

However, sbuild successfully satisfies the dependency: libz-dev is a
virtual package provided by zlib1g-dev (only), and sbuild seems to
interpret it as equivalent to zlib1g-dev:native, which is satisfiable.
britney should probably do the same.

I've also opened a ghostscript bug recommending that the B-D should be
swapped to the more canonical form zlib1g-dev:native to work around this.

    smcv