disable command buffer on iOS g3 builds

Change-Id: Iaed8c2101255c5e02333af76a19b32031da45a48
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/275641
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/public.bzl b/public.bzl
index 8168055..ee571bb 100644
--- a/public.bzl
+++ b/public.bzl
@@ -703,6 +703,7 @@
                 "SK_BUILD_FOR_IOS",
                 "SK_BUILD_NO_OPTS",
                 "SKNX_NO_SIMD",
+                "SK_NO_COMMAND_BUFFER",  # Test tools that use thread_local.
             ],
             # WASM
             [