Attempt to heal MacToT bots.

See https://github.com/erikdoe/ocmock/issues/369

TBR=rnk

Bug: none
Change-Id: Ice9aca9e524d54eecb4bb41615f36c9926de1e2e
Reviewed-on: https://chromium-review.googlesource.com/c/1394430Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619636}

third_party/ocmock/BUILD.gn

@@ -13,6 +13,9 @@ config("ocmock_warnings") {
   cflags = [
     "-Wno-semicolon-before-method-body",
     "-Wno-undeclared-selector",
+
+    # https://github.com/erikdoe/ocmock/issues/369
+    "-Wno-incompatible-pointer-types",
   ]
 }