just running ./configure I can make without any problems.

but when ./configure --with-nsapi=/netscape/server4 it configures fine but as soon as I run make, here is what I get:

Making all in Zend
        cd .. \
          && CONFIG_FILES=Zend/Makefile CONFIG_HEADERS= /bin/sh ./config.status
creating Zend/Makefile
        /bin/sh ../libtool --silent --mode=compile c++ -DHAVE_CONFIG_H -I. -I. -I
..   -D_REENTRANT -DXML_BYTE_ORDER=21 -I../TSRM -DTHREAD=1   -c zend-scanner-cc.c
c
In file included from /usr/include/unistd.h:11,
                 from ./zend-scanner.l:71:
/usr/include/sys/unistd.h:188: declaration of C function `int pthread_atfork(void
 (*)(...), void (*)(...), void (*)(...))' conflicts with
/usr/include/sys/pthread.h:440: previous declaration `int pthread_atfork(void (*)
(), void (*)(), void (*)())' here
*** Error exit code 1

Stop.
*** Error exit code 1

Stop.