[Serusers] error compiling ser 0.8.11 on Solaris 2.8 using gcc 3.3

[Ziying Sherwin]

We are trying to compile ser 0.8.11 on Solaris 2.8 using gcc 3.3. Since
we don't have librt.so on our system, we change the Makefile.defs to use
libpthread instead, we also added "<sched.h>" to be inclueded in the 
main.c file. However, during the compilation, we still got the error message:

Extra objs: 
gcc  -O2  action.o crc.o data_lump.o data_lump_rpl.o dprint.o dset.o error.o fifo_server.o flags.o forward.o hash_func.o ip_addr.o main.o md5.o md5utils.o modparam.o msg_translator.o pass_fd.o proxy.o receive.o resolve.o route.o route_struct.o script_cb.o sr_module.o stats.o tcp_main.o tcp_read.o timer.o udp_server.o mem/f_malloc.o mem/mem.o mem/memtest.o mem/q_malloc.o mem/shm_mem.o mem/vq_malloc.o parser/hf.o parser/msg_parser.o parser/parse_content.o parser/parse_cseq.o parser/parse_event.o parser/parse_expires.o parser/parse_fline.o parser/parse_from.o parser/parse_hname2.o parser/parse_hostport.o parser/parse_nameaddr.o parser/parse_param.o parser/parse_rr.o parser/parse_to.o parser/parse_uri.o parser/parse_via.o parser/parser_f.o parser/digest/digest.o parser/digest/digest_parser.o parser/digest/param_parser.o parser/contact/contact.o parser/contact/parse_contact.o db/db.o lex.yy.o cfg.tab.o     -lfl -ldl -lresolv -L/usr/local/lib -lfl -lxnet -lpthread -lnsl  -o ser 
Undefined                       first referenced
 symbol                             in file
sched_yield                         main.o
ld: fatal: Symbol referencing errors. No output written to ser
collect2: ld returned 1 exit status
make: *** [ser] Error 1
 
Do we really need librt.so? Which GNU package does that come from? Are there
anyone who successfully install ser 0.8.11 on Solaris?

Thanks very much.
Ziying Sherwin