negative performance speedup with -fno-plt

[Florian Weimer]

* Farid Zakaria:

> Thank you for the advice; I will look into that with perf if it has statistics.
>
> I noticed also that I had only built python + libpython without a PLT
> but glibc itself continued to have a PLT
> (I'm using NixOS to make changes).
>
> Looks like trying to override CFLAGS to build glibc without PLT is
> challenging; it didn't like me just setting CFLAGS :)

Passing CC="gcc -fno-plt" should work for building, but there will be
new test suite failures due to -fno-plt.

Thanks,
Florian