[PATCH v2] change ifunc assembly test to a link test

[Roland McGrath]

> so just change "asm" to "ld" ?  e.g. libc_cv_ld_gnu_indirect_function

I guess that's fine.  Don't forget to change the message.

> hmm, current code is already using such features:
> $ grep 'grep -q' configure.in 
> if $CC -v -static-libgcc 2>&1 | grep -q 'unrecognized option.*static-libgcc';      
> conftest.c -v 2>&1 >/dev/null | grep -q " -lunwind "; then
>    && grep -q .note.GNU-stack conftest.s \

It shouldn't be.  Don't make it worse.  Follow the configure standards.