Tail of the build output:

[3046/3341] Linking default/source3/libsmbconf.so
default/source3/lib/pthreadpool/pthreadpool_1.o: In function `pthreadpool_prep_atfork':
pthreadpool.c:(.text+0x794): undefined reference to `pthread_atfork'
collect2: ld returned 1 exit status
Waf: Leaving directory `/share/1000/src/samba-4.0.0/bin'
Build failed:  -> task failed (err #1):
        {task: cc_link util_34.o,pthreadpool_1.o,system_55.o,sendfile_55.o,recvfile_55.o,time_55.o,util_sid_55.o,util_file_55.o,util_55.o,util_sock_55.o,util_transfer_file_55.o,sock_exec_55.o,loadparm_ctx_35.o,version_107.o,ndr_messaging_3.o,messages_56.o,messages_local_56.o,messages_ctdbd_56.o,ctdb_packet_56.o,ctdbd_conn_56.o,ctdb_conn_56.o,msg_channel_56.o,id_cache_56.o,talloc_dict_56.o,serverid_56.o,addrchange_56.o,dbwrap_open_56.o,dbwrap_ctdb_56.o,dbwrap_watch_56.o,g_lock_56.o,debug_s3_56.o,dumpcore_56.o,interface_56.o,username_56.o,access_56.o,smbrun_56.o,wins_srv_56.o,substitute_56.o,substitute_generic_56.o,ms_fnmatch_56.o,tallocmsg_56.o,dmallocmsg_56.o,lang_tdb_56.o,gencache_56.o,events_56.o,server_contexts_56.o,server_prefork_56.o,server_prefork_util_56.o,ldap_escape_56.o,fncall_56.o,krb5_errs_56.o,system_smbd_56.o,audit_56.o,tevent_wait_56.o,idmap_cache_56.o,loadparm_37.o,sharesec_37.o,ldap_debug_handler_37.o,util_names_37.o,smbconf_init_76.o,smbconf_reg_76.o,util_pw_40.o,reg_backend_smbconf_46.o,reg_init_smbconf_46.o,reg_util_token_46.o,reg_api_util_46.o,smbconf_1.o,smbconf_txt_1.o,smbconf_util_1.o -> libsmbconf.so}
make: *** [all] Error 1

May be a "-pthread" vs "-lpthread" issue since:

$ nm /opt/armv5tejl-unknown-linux-gnueabi/lib/libpthread-2.3.6.so | grep atfork
00009560 t __dyn_pthread_atfork
         U __register_atfork@@GLIBC_2.4
00009560 T pthread_atfork@GLIBC_2.4