gnuradio: depends on shared libs

volk must be compiled with toolchain built with shared lib to avoid :
attempted static link of dynamic object `../lib/libvolk.so.0.0.0'

[Thomas:
 - rebase after the non-largefile removal.
 - comment must be "dynamic library" not "shared library".]

Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>