While looking at #739308 and its effect on other packages, I noticed that
cmake_libzip_zipconf_path.diff searches ${libdir} for zipconf.h.
libzip ships a pkg-config file, libzip.pc: it would be better to
use that, which should always result in use of the header and library
paths that the libzip upstream developer or Debian maintainer intend
to be used.

See also:
http://www.cmake.org/cmake/help/v3.0/module/FindPkgConfig.html

or if you (or the upstream developer) don't want to rely exclusively on
pkg-config,
http://www.cmake.org/Wiki/CMake:How_To_Find_Libraries#Writing_find_modules

(It might be worth asking the upstream developer of libzip whether
they consider their "build API" to be "you are expected to always use
pkg-config", like GLib and libdbus, or more like "pkg-config is an
optional convenience".)

Regards,
    S