Flip nacl sdk bots to use MB to generate the build files.

scripts/slave/recipes/nacl/sdk.expected/basic.json

Index: scripts/slave/recipes/nacl/sdk.expected/basic.json
diff --git a/scripts/slave/recipes/nacl/sdk.expected/basic.json b/scripts/slave/recipes/nacl/sdk.expected/basic.json
index 5d6d75ee94ee7e7be1fe919bf969b4e6b3900060..1f97985596650119da0af02dfce3e16536b0d339 100644
--- a/scripts/slave/recipes/nacl/sdk.expected/basic.json
+++ b/scripts/slave/recipes/nacl/sdk.expected/basic.json
@@ -114,6 +114,7 @@
     "cwd": "[SLAVE_BUILD]/src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
+      "GYP_CHROMIUM_NO_ACTION": "1",
       "GYP_DEFINES": "component=static_library gomadir='[BUILD]/goma' target_arch=x64 use_goma=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
@@ -123,6 +124,27 @@
     "cmd": [
       "python",
       "-u",
+      "[SLAVE_BUILD]/src/tools/mb/mb.py",
+      "gen",
+      "-m",
+      "chromium.testing.master",
+      "-b",
+      "TestBuilder",
+      "--config-file",
+      "[SLAVE_BUILD]/src/tools/mb/mb_config.pyl",
+      "--goma-dir",
+      "[BUILD]/goma",
+      "//out/Release"
+    ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
+    },
+    "name": "generate_build_files"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py",
       "--show-path",
       "python",