Bump Clang ToT timeouts to 14 hours

Some configurations are hitting the current 12 hour timeout limit, like
the ToT Clang Mac ASan bot.

Bug: 1151435
Change-Id: I3527d18ddfb0d135ea8afc5e66e35d42d758e416
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2553186Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829916}

infra/config/lib/ci.star

@@ -521,7 +521,7 @@ def clang_builder(*, name, builderless = True, cores = 32, properties = None, **
         # Because these run ToT Clang, goma is not used.
         # Naturally the runtime will be ~4-8h on average, depending on config.
         # CFI builds will take even longer - around 11h.
-        execution_timeout = 12 * time.hour,
+        execution_timeout = 14 * time.hour,
         properties = properties,
         **kwargs
     )