perf tools: Fix buildid processing

After recording, 'perf record' post-processes the data to determine
which buildids are needed.

That processing must process the data in time order, if possible,
because otherwise dependent events, like forks and mmaps, will not make
sense.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1439994561-27436-4-git-send-email-adrian.hunter@intel.com


[ Moved the sample_id_add to after trying to open the events, use pr_warning ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>