The problem is that libatk1.0-dev depends on libc6-dev, which causes this breakage. Thus currently adding any package that depends on libc6-dev directly or indirectly (libatk1.0-dev -> libglib2.0-dev -> zlib1g-dev -> libc6-dev) breaks this way. I bet that is a lot of packages that are currently unusable in snap.
The problem is that libatk1.0-dev depends on libc6-dev, which causes this breakage. Thus currently adding any package that depends on libc6-dev directly or indirectly (libatk1.0-dev -> libglib2.0-dev -> zlib1g-dev -> libc6-dev) breaks this way. I bet that is a lot of packages that are currently unusable in snap.