Do not use MB for Clang Upload bots.

scripts/slave/recipe_modules/chromium/config.py

Index: scripts/slave/recipe_modules/chromium/config.py
diff --git a/scripts/slave/recipe_modules/chromium/config.py b/scripts/slave/recipe_modules/chromium/config.py
index ee8a617ac39e3790a597a1f2f2dc2375d39194a1..b17fda398f9ee8e47ad7525ff978695b59090f7b 100644
--- a/scripts/slave/recipe_modules/chromium/config.py
+++ b/scripts/slave/recipe_modules/chromium/config.py
@@ -72,6 +72,7 @@ def BaseConfig(HOST_PLATFORM, HOST_ARCH, HOST_BITS,
       PATH = List(Path),
       ADB_VENDOR_KEYS = Single(Path, required=False),
       LLVM_FORCE_HEAD_REVISION = Single(basestring, required=False),
+      LLVM_FORCE_LOCAL_BUILD = Single(basestring, required=False),
       GOMA_STUBBY_PROXY_IP_ADDRESS = Single(basestring, required=False),
     ),
     project_generator = ConfigGroup(
@@ -545,6 +546,10 @@ def clang_tot(c):
   if c.TARGET_PLATFORM != 'win':
     c.gyp_env.GYP_DEFINES['clang_use_chrome_plugins'] = 0
 
+@config_ctx()
+def clang_upload(c):
+  c.env.LLVM_FORCE_LOCAL_BUILD = 'YES'
+
 @config_ctx(includes=['ninja', 'clang', 'asan', 'static_library'])
 def win_asan(c):
   # These are set on the lkgr bot, and the fyi bots should match the lkgr bot.