irix6.5 bootstrap failure in all-target-libiberty - ranlib not found

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

irix6.5 bootstrap of mainline with CC=gcc fails building all-target-libiberty with

rm -f libiberty.a pic/libiberty.a
ar rc libiberty.a \
  regex.o cplus-dem.o cp-demangle.o md5.o alloca.o argv.o choose-temp.o concat.o dyn-string.o fdmatch.o fibheap.o floatformat.o fnmatch.o getopt.o getopt1.o getpwd.o getruntime.o hashtab.o hex.o lbasename.o make-relative-prefix.o make-temp-file.o objalloc.o obstack.o partition.o pexecute.o safe-ctype.o sort.o spaces.o splay-tree.o strerror.o strsignal.o ternary.o xatexit.o xexit.o xmalloc.o xmemdup.o xstrdup.o xstrerror.o  asprintf.o basename.o mkstemps.o setenv.o vasprintf.o vfork.o
ranlib libiberty.a
make[2]: ranlib: Command not found

Irix 6.5 doesn't have ranlib, but somehow the RANLIB=: substitution isn't working.