Add a BoringSSL builder for OPENSSL_NO_THREADS.

masters/master.client.boringssl/slaves.cfg

 # -*- python -*-
 # ex: set syntax=python:
 
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 linux_slave_builder_map = {
   '44': ['linux', 'linux_shared', 'linux32', 'linux_noasm_asan', 'linux_small',
-         'docs'],
+         'linux_nothreads', 'docs'],
 }
 
 win_slave_builder_map = {
   '131': ['win64', 'win64_small', 'win32', 'win32_small'],
 }
 
 mac_slave_builder_map = {
   '2': ['mac', 'mac_small'],
 }
 
@@ skipping 25 matching lines @@
     'master': 'Boringssl',
     'builder': builders,
     'hostname': 'vm%s-m3' % host,
     'os': 'mac',
     'version': '10.9',
     'bits': '64',
   } for host, builders in mac_slave_builder_map.iteritems()
 ]
 
 slaves = linux_slaves + win_slaves + mac_slaves