The following bug has been logged online:

Bug reference: 1627
Logged by: John Danger
Email address: mr1mavin (AT) yahoo (DOT) com
PostgreSQL version: 8.0.2
Operating system: Mac OSX 10.4
Description: Fails to compile
Details:

While I don't have extensive experience with compiling software, I followed
the basic steps under Mac OSX 10.3 without any problems, but with 10.4 the
following occurs during make...

gcc -no-cpp-precomp -O2 -Wall -Wmissing-prototypes -Wpointer-arith
-Wendif-labels -fno-strict-aliasing -DFRONTEND -I. -I../../../src/include
-I/sw/include/ -I../../../src/port -c -o thread.o thread.c
ar crs libpq.a `lorder fe-auth.o fe-connect.o fe-exec.o fe-misc.o fe-print.o
fe-lobj.o fe-protocol2.o fe-protocol3.o pqexpbuffer.o pqsignal.o fe-secure.o
md5.o ip.o wchar.o encnames.o noblock.o pgstrcasecmp.o thread.o | tsort`
usage: join [-a fileno | -v fileno ] [-e string] [-1 field] [-2 field]
[-o list] [-t char] file1 file2
ranlib libpq.a
gcc -no-cpp-precomp -O2 -Wall -Wmissing-prototypes -Wpointer-arith
-Wendif-labels -fno-strict-aliasing -dynamiclib -install_name
/usr/local/pgsql/lib/libpq.4.dylib -compatibility_version 4 -current_version
4.0 -multiply_defined suppress fe-auth.o fe-connect.o fe-exec.o fe-misc.o
fe-print.o fe-lobj.o fe-protocol2.o fe-protocol3.o pqexpbuffer.o pqsignal.o
fe-secure.o md5.o ip.o wchar.o encnames.o noblock.o pgstrcasecmp.o thread.o
-L../../../src/port -L/sw/lib -lresolv -o libpq.4.0.dylib
/usr/bin/libtool: for architecture: cputype (16777234) cpusubtype (0) file:
-lSystem is not an object file (not allowed in a library)
make[3]: *** [libpq.4.0.dylib] Error 1
make[2]: *** [all] Error 2
make[1]: *** [all] Error 2
make: *** [all] Error 2

---------------------------(end of broadcast)---------------------------
TIP 5: Have you checked our extensive FAQ?

http://www.postgresql.org/docs/faq