gpsd: disallow profiling support with uClibc toolchain

The following problem was reported by Thomas Petazzoni.

If BR2_PACKAGE_GPSD_PROFILING is enabled with a uClibc-based toolchain, then
gpsd fails to build. See the following for details.

  http://autobuild.buildroot.org/results/be707893f4bf0e7e964d183e4a655c5bb72d1889/build-end.log
  http://autobuild.buildroot.org/results/be707893f4bf0e7e964d183e4a655c5bb72d1889/defconfig

.

The issue is that uClibc lacks the necessary infrastructure to support
profiling. This patch disallows selection of the gpsd profiling feature when
a uClibc-based toolchain is selected.

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