When building netatalk with clang as cc (I haven't tried with GCC), afpd fails to link with the following error:

libtool: link: cc -I../../include -I../../sys -I/usr/local/include -DAPPLCNAME -DSERVERTEXT=\"/usr/local/etc/msg/\" -D_PATH_AFPDDEFVOL=\"/usr/local/etc/AppleVolumes.default\" -D_PATH_AFPDSYSVOL=\"/usr/local/etc/AppleVolumes.system\" -D_PATH_AFPDPWFILE=\"/usr/local/etc/afppasswd\" -D_PATH_AFPDCONF=\"/usr/local/etc/afpd.conf\" -D_PATH_AFPDSIGCONF=\"/usr/local/etc/afp_signature.conf\" -D_PATH_AFPDUAMPATH=\"/usr/local/libexec/netatalk-uams/\" -D_PATH_ACL_LDAPCONF=\"/usr/local/etc/afp_ldap.conf\" -D_PATH_AFPDUUIDCONF=\"/usr/local/etc/afp_voluuid.conf\" -I../../include "-D_U_=__attribute__((unused))" -O2 -pipe -I/usr/local/include -fno-strict-aliasing -I../../sys -o afpd afpd-afp_asp.o afpd-afp_avahi.o afpd-afp_config.o afpd-afp_dsi.o afpd-afp_mdns.o afpd-afp_options.o afpd-afp_util.o afpd-afp_zeroconf.o afpd-afprun.o afpd-afs.o afpd-appl.o afpd-auth.o afpd-catsearch.o afpd-desktop.o afpd-dircache.o afpd-directory.o afpd-enumerate.o afpd-extattrs.o afpd-fce_api.o afpd-fce_util.o afpd-file.
 o afpd-filedir.o afpd-fork.o afpd-gettok.o afpd-hash.o afpd-main.o afpd-mangle.o afpd-messages.o afpd-nfsquota.o afpd-ofork.o afpd-quota.o afpd-status.o afpd-switch.o afpd-uam.o afpd-uid.o afpd-unix.o afpd-volume.o afpd-acls.o -Wl,--export-dynamic  -L/usr/local/lib ../../libatalk/cnid/.libs/libcnid.a -L../../../libatalk -L../../libatalk ../../libatalk/.libs/libatalk.a -L../libatalk /usr/local/lib/libgcrypt.so /usr/local/lib/libgpg-error.so /usr/local/lib/libintl.so /usr/local/lib/libiconv.so -ldns_sd /usr/local/lib/libslp.so -lcrypto -lwrap -Wl,-rpath -Wl,/usr/local/lib -Wl,-rpath -Wl,/usr/local/lib
afpd-file.o: In function `afp_exchangefiles':
file.c:(.text+0x3305): warning: warning: mktemp() possibly used unsafely; consider using mkstemp()
afpd-afp_mdns.o: In function `md_zeroconf_register':
afp_mdns.c:(.text+0x775): undefined reference to `pthread_create'
cc: error: linker command failed with exit code 1 (use -v to see invocation)
gmake[3]: *** [afpd] Erreur 1
gmake[3] : on quitte le répertoire « /usr/obj/usr/ports/net/netatalk/work/netatalk-2.2.3/etc/afpd »
gmake[2]: *** [all-recursive] Erreur 1
gmake[2] : on quitte le répertoire « /usr/obj/usr/ports/net/netatalk/work/netatalk-2.2.3/etc »
gmake[1]: *** [all-recursive] Erreur 1
gmake[1] : on quitte le répertoire « /usr/obj/usr/ports/net/netatalk/work/netatalk-2.2.3 »
gmake: *** [all] Erreur 2
*** [do-build] Error code 1

Stop in /usr/ports/net/netatalk.
*** [build] Error code 1

Stop in /usr/ports/net/netatalk.

Fix: Explicitly set PTHREAD_LIBS in the Makefile.

Patch attached with submission follows:
How-To-Repeat: build netatalk with zeroconf enabled

cd /usr/ports/net/netatalk && make install