buildroot

android-tools: needs thread support

Both adb and adbd use <pthread.h>, and fastboot needs thread due to
its dependency on libselinux, so we put the dependency in the
top-level android-tools Config.in option.

Fixes:

  http://autobuild.buildroot.net/results/bafadedc0ae91f8a1e26d14f30b37d6bb9486816/

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