force use of system zlib instead of bundled G4zlib
--- source/visualization/HepRep/sources.cmake.orig	2011-12-02 15:07:49.000000000 +0000
+++ source/visualization/HepRep/sources.cmake	2011-12-18 06:21:22.000000000 +0000
@@ -91,7 +91,7 @@
         G4specsolids
         G4tracking
         G4vis_management
-        G4zlib
+        ${ZLIB_LIBRARIES}
     GLOBAL_DEPENDENCIES
         G4digits_hits
         G4geometry
@@ -102,7 +102,7 @@
         G4modeling
         G4tracking
         G4vis_management
-        G4zlib
+        ${ZLIB_LIBRARIES}
     LINK_LIBRARIES
 )
 
--- source/visualization/externals/gl2ps/sources.cmake.orig	2011-12-02 16:07:56.000000000 +0100
+++ source/visualization/externals/gl2ps/sources.cmake	2012-03-09 14:09:26.965148002 +0100
@@ -49,9 +49,9 @@
         G4OpenGL2PSAction.cc
         gl2ps.cc
     GRANULAR_DEPENDENCIES
-        G4zlib
+        ${ZLIB_LIBRARIES}
     GLOBAL_DEPENDENCIES
-        G4zlib
+        ${ZLIB_LIBRARIES}
     LINK_LIBRARIES
         ${OPENGL_LIBRARIES}
 )