[BUILD] Check for sqrt in libm.
[BUILD] Check for sqrt in libm.

- Was working without that up until now but on a native build on pclinux
  with gcc 4.8 it caused troubles when linking an application using
  libARStream.

Change-Id: Id83e3cd931bc5e9b315bff025522f1492e4993a0
Reviewed-on: https://gerrit.parrot.biz/19597
Reviewed-by: Nicolas Brulez <c7b4d7ddc34318e865922d5ddc9ce680dfb1b14c@parrot.com>

Parrot-Developers/libARStream,Parrot-Developers/libARStream,Parrot-Developers/libARStream