libtool 1.5 broken on Tru64

[Bruno Haible]

This happens on with libtool-1.5 on Tru64, when GNU libiconv-1.9 is
configured with CC="cc -O" CFLAGS="":

$ /bin/sh ../libtool --mode=link cc -O ./iconv.c 
./../libcharset/lib/localcharset.c ./relocatable.c -c -o iconv_plug.o
/bin/ld -r -o iconv_plug.o   
Error: No object file linked

$ /bin/sh ../libtool --mode=link cc ./iconv.c 
./../libcharset/lib/localcharset.c ./relocatable.c -c -o iconv_plug.o
libtool: link: unable to infer tagged configuration
libtool: link: specify a tag with `--tag'

And when configured with CC="cc" CFLAGS="-O":

$ /bin/sh ../libtool --mode=link cc ./iconv.c 
./../libcharset/lib/localcharset.c ./relocatable.c -c -o iconv_plug.o
/bin/ld -r -o iconv_plug.o   
Error: No object file linked

Apparently libtool understands well that I want to create a .o from
several other object files (not giving "-shared"!) but it fails to
emit the right commands.

Bruno