Add a BoringSSL builder for OPENSSL_NO_THREADS.

scripts/slave/recipes/boringssl.expected/linux_nothreads.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "client.boringssl",
       "--builder",
-      "linux_shared",
+      "linux_nothreads",
       "--slave",
       "slavename",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': 'util/bot/DEPS', 'managed': True, 'name': 'boringssl', 'url': 'https://boringssl.googlesource.com/boringssl.git'}]",
       "--root",
       "boringssl",
       "--revision_mapping_file",
       "{}",
       "--git-cache-dir",
       "[GIT_CACHE]",
@@ skipping 78 matching lines @@
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/boringssl/util/bot/go/env.py",
       "[SLAVE_BUILD]/boringssl/util/bot/cmake-linux64/bin/cmake",
       "-GNinja",
-      "-DBUILD_SHARED_LIBS=1",
+      "-DCMAKE_CXX_FLAGS=-DOPENSSL_NO_THREADS=1",

[svaldez, 2016/04/28 18:36:58]

Can you just use C_CXX_FLAGS?

[davidben, 2016/04/28 18:46:04]

I don't think that currently keeps the old value. We could (should?) probably
make our own BORINGSSL_C_COMMON_FLAGS knob at some point. *shrug*

+      "-DCMAKE_C_FLAGS=-DOPENSSL_NO_THREADS=1",
       "[SLAVE_BUILD]/boringssl"
     ],
     "cwd": "[SLAVE_BUILD]/boringssl/build",
     "name": "cmake"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/boringssl/util/bot/go/env.py",
@@ skipping 114 matching lines @@
       "@@@STEP_LOG_LINE@test_utils.test_results@}@@@",
       "@@@STEP_LOG_END@test_utils.test_results@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]