oeqa.buildperf: be sure to use the latest buildstats

Be sure to take the latest buildstats if multiple buildstats are found.

(From OE-Core rev: bad495f0d0144728a0132c3d3c4d98c24ead4afd)

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/buildperf/base.py

@@ -466,7 +466,7 @@ class BuildPerfTestCase(unittest.TestCase):
             return bs_json
 
         log.info('Saving buildstats in JSON format')
-        bs_dirs = os.listdir(self.bb_vars['BUILDSTATS_BASE'])
+        bs_dirs = sorted(os.listdir(self.bb_vars['BUILDSTATS_BASE']))
         if len(bs_dirs) > 1:
             log.warning("Multiple buildstats found for test %s, only "
                         "archiving the last one", self.name)