Bug#766375: lintian: false positive with arch-qualified build-depends

[Wookey <wookey@wookware.org>]

Package: lintian
Version: 2.5.28
Severity: normal

It seems that Lintian does not understand arch-qualified dependencies,
or build-dependencies.

If a package has an arch-qualified build-dependency on a
build-essential package, such as on libc:armhf, then lintian complains
about depends-on-build-essential-package-without-using-version

But when the dependency is on a package from a foreign arch this is
not wrong. This applies to both build-deps and deps.

An example package which triggers this is cross-gcc-4.9-armel (currently in NEW).