Can't build libpq test example

Can anyone help me with this problem?

I have installed postgresql-7.2.1 and am trying to compile one of the
test programs from the directory src/test/examples.

I am running an old version of SCO Openserver 5

I am using the following command:

cc testlibpq.c -I/usr/local/pgsql/include -L/usr/local/pgsql/lib -lpq
-otestlibpq

I receive the following error messages:

undefined first referenced
symbol in file
PQfinish testlibpq.o
PQsetdbLogin testlibpq.o
PQstatus testlibpq.o
PQerrorMessage testlibpq.o
PQexec testlibpq.o
PQresultStatus testlibpq.o
PQclear testlibpq.o
PQnfields testlibpq.o
PQfname testlibpq.o
PQgetvalue testlibpq.o
PQntuples testlibpq.o
ld fatal: Symbol referencing errors. No output written to testlibpq