Add support for SwiftWasm

[yonihemi]

Use WASILibc module for random when running in SwiftWasm.

How to run

• Install a recent SwiftWasm toolchain.
• Clone the Dealer package:

git clone https://github.com/apple/example-package-dealer.git

• Using the SwiftWasm toolchain, build the package:

cd example-package-dealer
swift build -c release --triple wasm32-unknown-wasi

• Install a runtime such as Wasmer.
• Run the WebAssembly module:

wasmer .build/wasm32-unknown-wasi/release/Dealer.wasm