Enable sandboxing for swift builds
Enable sandboxing for swift builds

I discovered an issue in the rules where we were relying on the fact
that persistent workers, which rules_swift uses, disable the sandbox by
default. Disabling workers in these rules shouldn't hurt anything since
we don't rely on the incremental compilation performance benefits.

bazelbuild/rules_apple,bazelbuild/rules_apple,bazelbuild/rules_apple,bazelbuild/rules_apple