Here's the bot:
https://uberchromegw.corp.google.com/i/chromeos/builders/veyron_rialto-chrome-pfq

First failing build:
https://uberchromegw.corp.google.com/i/chromeos/builders/veyron_rialto-chrome-pfq/builds/550

Most recent failing build:
https://uberchromegw.corp.google.com/i/chromeos/builders/veyron_rialto-chrome-pfq/builds/556


Looks like the build is taking too long?

Log snippet:
@@@STEP_FAILURE@@@
02:14:19: ERROR: Timeout occurred- waited 4701 seconds, failing. Timeout reason: This build has reached the timeout deadline set by the master. Either this stage or a previous one took too long (see stage timing historical summary in ReportStage) or the build failed to start on time.
cros_sdk: Signaled to shutdown: caught 15 signal.

@@@STEP_FAILURE@@@
02:14:19: ERROR: Traceback (most recent call last):
  File "/b/cbuild/internal_master/chromite/cbuildbot/stages/generic_stages.py", line 525, in Run
    self.PerformStage()
  File "/b/cbuild/internal_master/chromite/cbuildbot/stages/build_stages.py", line 331, in PerformStage
    extra_env=self._portage_extra_env)
  File "/b/cbuild/internal_master/chromite/cbuildbot/commands.py", line 482, in Build
    enter_chroot=True)
  File "/b/cbuild/internal_master/chromite/cbuildbot/commands.py", line 139, in RunBuildScript
    raise failures_lib.BuildScriptFailure(ex, cmd[0])
  File "/b/cbuild/internal_master/chromite/cbuildbot/commands.py", line 124, in RunBuildScript
    return runcmd(cmd, **kwargs)
  File "/b/cbuild/internal_master/chromite/lib/cros_build_lib.py", line 594, in RunCommand
    (cmd_result.output, cmd_result.error) = proc.communicate(input)
  File "/usr/lib/python2.7/subprocess.py", line 751, in communicate
    self.wait()
  File "/usr/lib/python2.7/subprocess.py", line 1291, in wait
    pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
  File "/usr/lib/python2.7/subprocess.py", line 478, in _eintr_retry_call
    return func(*args)
  File "/b/cbuild/internal_master/chromite/lib/timeout_util.py", line 131, in kill_us
    raise SystemExit(error_message)
SystemExit: Timeout occurred- waited 4575 seconds, failing. Timeout reason: This build has reached the timeout deadline set by the master. Either this stage or a previous one took too long (see stage timing historical summary in ReportStage) or the build failed to start on time.