build_status: Increase timeout for build start

The timeout for a build to start is 5 minutes.  With timeouts in place
today for the overall build, increasing this timeout to allow for some
queuing on the swarming side is reasonable.  This is primarily due to
release builders causing overruns that have resulted in bot shortages.

BUG=chromium:976707
TEST=`cros_sdk -- /mnt/host/source/chromite/run_tests`

Change-Id: I80207f8f1f22f54bfa70dcf6be9506bc3b2a4c9f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1667536
Reviewed-by: Dhanya Ganesh <dhanyaganesh@chromium.org>
Tested-by: Mike Nichols <mikenichols@chromium.org>
Commit-Queue: Mike Nichols <mikenichols@chromium.org>
diff --git a/cbuildbot/build_status.py b/cbuildbot/build_status.py
index 1529cfc..4e3b82e 100644
--- a/cbuildbot/build_status.py
+++ b/cbuildbot/build_status.py
@@ -31,7 +31,7 @@
   it will only interpret slave statuses by querying CIDB.
   """
 
-  BUILD_START_TIMEOUT_MIN = 5
+  BUILD_START_TIMEOUT_MIN = 30
 
   ACCEPTED_STATUSES = (constants.BUILDER_STATUS_PASSED,
                        constants.BUILDER_STATUS_SKIPPED,)