So far there's only x86 libdw unwind support merged in perf.
Disable it on all other architectures in case libdw unwind
support is detected in system.

Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1397988006-14158-1-git-send-email-jolsa@redhat.comSigned-off-by: Jiri Olsa <jolsa@redhat.com>