Use debug options from flags instead of ExecutableBuildOptions to extract HloShardingV3 flag because we are planning to enable/disable this flag by default in debug options and if some JAX users wants to disable they can do it via XLA_FLAGS

Use debug options from flags instead of ExecutableBuildOptions to extract HloShardingV3 flag because we are planning to enable/disable this flag by default in debug options and if some JAX users wants to disable they can do it via XLA_FLAGS #161219