Random seems broken in Javy

[jianghong]

Given a JS source file that looks like:

console.log(Math.random())

I see the following output:

➜  javy git:(main) target/release/javy compile index.js -o index.wasm                                                                   
➜  javy git:(main) wasmtime run index.wasm
0.6111985957948094
➜  javy git:(main) wasmtime run index.wasm
0.6111985957948094

Running the same module with a random call multiple times results in the same output. Random should not be deterministic when not using a deterministic-wasi-ctx.