Linux Archive - gentoo prefix: dev-libs/libxml2 tries to link to system zlib

Hi,

I have the following problem with my gentoo prefix installation on
CentOS (amd64): Emerging dev-libs/libxml2-2.7.8-r2 fails with the
following error:
...
libtool: link: x86_64-pc-linux-gnu-gcc -O2 -pipe -march=native
-pedantic -W -Wformat -Wunused -Wimplicit -Wreturn-type -Wswitch
-Wcomment -Wtrigraphs -Wformat -Wchar-subscripts -Wuninitialized
-Wparentheses -Wshadow -Wpointer-arith -Wcast-align -Wwrite-strings
-Waggregate-return -Wstrict-prototypes -Wmissing-prototypes
-Wnested-externs -Winline -Wredundant-decls -Wl,-O1 -o
.libs/testAutomata testAutomata.o ./.libs/libxml2.so -ldl -lz -lm
-Wl,-rpath -Wl,/local_mount/space/megcon/3/users/mluessi/gentoo/usr/lib
./.libs/libxml2.so: undefined reference to `gzopen64'
...

It seems like the linker is trying to the system "libz.so" (which does
not have "gzopen64") instead of the "libz.so" in the prefix:

system:
objdump -T /usr/lib/libz.so.1 | grep gzopen
00815810 g DF .text 00000014 Base gzopen

in prefix:
objdump -T $EPREFIX/lib/libz.so.1.2.5 | grep gzopen
0000000000006320 g DF .text 000000000000000d Base gzopen
0000000000006310 g DF .text 000000000000000d ZLIB_1.2.3.3 gzopen64

What's a bit strange is that "$EPREFIX/lib" is not in the library
search path. I tried copying "$EPREFIX/lib/libz.so.1.2.5" into
"$EPREFIX/usr/lib/" but it doesn't help (and it would be an ugly
solution anyways).

It seems like this
http://www.mail-archive.com/gentoo-alt@lists.gentoo.org/msg05874.html
is the same problem. Unfortunately no solution was posted. Does anyone
have an idea how to fix this?

Thanks,

Martin