[LLVM Monitor] Sort builds by number to find most recent

The data returned by the buildbot looks like it is sorted by build
number, but it isn't actually, so we need to do the sorting ourselves.

Change-Id: Iac0febe60a4d3ac33ae018f708b22b0e37d2009d
diff --git a/monitor/bot-status.py b/monitor/bot-status.py
index 2536fa4..39fcb82 100755
--- a/monitor/bot-status.py
+++ b/monitor/bot-status.py
@@ -71,7 +71,7 @@
   builds = contents
 
   status = {}
-  reversed_builds = reversed(builds['builds'])
+  reversed_builds = iter(sorted(builds['builds'], key=lambda b: -b["number"]))
   for build in reversed_builds:
     if build['complete']:
       status['builderid'] = build['builderid']