`libpath_ops.dylib` should run natively on Apple Silicon arm machines

The `bin/cache/artifacts/engine/darwin-x64/libpath_ops.dylib` artifact dylib only contains a x64 slice, so runs with Rosetta on an arm64 Mac.  Ship a native arm64 variant to run on Apple Silicon host machines.

https://github.com/flutter/engine/pull/34267

@dnfield @zanderso 