this happens in 4.x.
3.x works fine and uses system-wide zlib-devel.
--
Summary: libgcj builds zlib subdir even if --with-system-zlib was
passed to ./configure
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: libgcj
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pluto at agmk dot net
CC: gcc-bugs at gcc dot gnu dot org,java-prs at gcc dot gnu
dot org
GCC build triplet: *
GCC host triplet: *
GCC target triplet: *
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22092