OK, the following works  for me:

>    Any additional libraries? [-lm -lc -lposix -lcrypt] -lm -lc -lcrypt

tho' I don't see how to set 'libswanted' from the command line.

The problem with rename() may be due to both libc.so and libposix.so
having a definition of "rename", and ld and ld.so disagreeing about
which is the right one to use....