package/libiio: fix python bindings without glibc utils

package/libiio: fix python bindings without glibc utils

Libiio python bindings use ctypes and specifically the find_library()
function from there to load the libiio.so shared library. This is not
working unless glibc utils (specifically ldconfig) is installed to the
target (alternatively the target would need gcc or binutils, for objdump
or ld).

The easy fix here is to just bypass the find_library() machinery
altogether as it's not needed on a buildroot system.

Signed-off-by: Marcus Hoffmann <buildroot@bubu1.eu>
Tested-by: Fiona Klute <fiona.klute@gmx.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>