ldd -u -r segfaults on some libs

[Roland McGrath]

> That's because ldd -u relocates only main, but not its dependent libs,
> so any use of _dl_vdso_vsym (through ifuncs) will run over an
> unrelocated GOT in libc.so.

It sure seems like all the mode==trace cases should not run ifunc selectors
at all.  That's running arbitrary code from the program rather than just
running ld.so code, which is a pretty big hole.


Thanks,
Roland