debian: build-dep on libz

debian/control

@@ -4,7 +4,7 @@ Priority: extra
 Maintainer: Autistici/Inventati <debian@autistici.org>
 Build-Depends: debhelper (>= 5), apache2-prefork-dev | apache2-threaded-dev,
  autoconf, automake, libtool, python-dev, python-support, swig,
- libpam-dev, python-setuptools, python-flup, pkg-config
+ libpam-dev, python-setuptools, python-flup, pkg-config, libz-dev
 Standards-Version: 3.7.2
 
 Package: ai-sso