google-breakpad: take into account host architecture dependencies

Building the target google-breakpad requires building the host variant
of google-breakpad. Just like the target google-breakpad only supports
a limited number of architectures, it is the same for the host
google-breakpad.

We therefore introduce a
BR2_PACKAGE_HOST_GOOGLE_BREAKPAD_ARCH_SUPPORTS option that is used
where necessary to prevent the user from choosing Google Breakpad when
building on unsupported host platforms.

Fixes:

  http://autobuild.buildroot.net/results/c7c04483508f9e4d629efa54571afeb1feaa5f73/


  (build on a powerpc64le machine)

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