bluez5_utils: not available with uClibc

Since the bump from 5.27 to 5.37 of bluez5_utils, the bluez code has
started using <wordexp.h> functionality. Unfortunately, our current
uClibc configuration does not have the wordexp functionality enabled,
so bluez5_utils cannot be built anymore.

In order to address this, we make bluez5_utils unavailable on
uClibc. This could be changed later by either removing the dependency
of bluez5_utils on wordexp support, or by deciding to add wordexp
support to our uClibc configuration.

Fixes:

  http://autobuild.buildroot.org/results/831/83112559d84dc156141339a31e3e02f1a2af5155/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>