Cannot bootstrap irix6.5 with --enable-threads=posix

["Billinghurst, David (CRTS)" <David dot Billinghurst at riotinto dot com>]

Can't bootstrap irix6.5 trunk or branch with  --enable-threads=posix

The stage1/xgcc cannot create executables since:
* libgcc.a(unwind-dw2.o) references pthread_once
* don't link with -lpthread

We need to add -lpthreads at the appropriate place.  Just before -lc works
fine.  I don't know how to do this.

For example:

stage1/xgcc -Bstage1/ -B/exd4/billingd/tmp/gcc/mips-sgi-irix6.5/bin/
--verbose  -DIN_GCC    -g -O2 -W -Wall -Wwrite-strings -Wstrict-prototypes
-Wmissing-prototypes -Wtraditional -pedantic -Wno-long-long  -DHAVE_CONFIG_H
-DGENERATOR_FILE  -o gengenrtl \
 gengenrtl.o  ` case "obstack.o" in ?*) echo obstack.o ;; esac ` ` case ""
in ?*) echo  ;; esac ` ` case "" in ?*) echo  ;; esac ` ` case "" in ?*)
echo  ;; esac ` ` case "" in ?*) echo  ;; esac ` ` case "" in ?*) echo  ;;
esac ` 
Reading specs from stage1/specs
Configured with: /exd4/billingd/src/gcc/configure --enable-shared
--enable-haifa --enable-threads=posix --prefix=/exd4/billingd/tmp/gcc
Thread model: posix
gcc version 3.0 20010526 (prerelease)
 stage1/collect2 -call_shared -no_unresolved -init __do_global_ctors -fini
__do_global_dtors -_SYSTYPE_SVR4 -woff 131 -n32 -o gengenrtl
/usr/lib32/mips3/crt1.o stage1/crtbegin.o -Lstage1 -L/usr/bin gengenrtl.o
obstack.o -dont_warn_unused -lgcc -warn_unused -L/usr/lib32/mips3
-L/usr/lib32 -dont_warn_unused -lc -warn_unused -dont_warn_unused -lgcc
-warn_unused stage1/crtend.o /usr/lib32/mips3/crtn.o
ld32: ERROR 33: Unresolved text symbol "pthread_once" -- 1st referenced by
stage1/libgcc.a(unwind-dw2.o).
        Use linker option -v to see when and which objects, archives and
dsos are loaded.  
ld32: INFO 152: Output file removed because of error.