[PATCH v3] change ifunc assembly test to a link test

[Roland McGrath]

> > This is subject to false-negatives if there is some unexpected weirdness
> > with readelf or something.  But I'm not too concerned.
> 
> yeah, that's why i sent the full readelf output to the log to make it
> easy to diagnose in the future.  i checked x86_64/arm/ia64 to make sure
> it was OK.

That was a good thing to do, certainly.  But what I have in mind is where
the test yields "no" and the person doing the build doesn't notice it, but
just builds a less-optimal library.