feat: add example4

__wasm/wasmtime/wasms/simple_rust_wasm/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "simple_rust_wasm"
+version = "0.1.0"

__wasm/wasmtime/wasms/simple_rust_wasm/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "simple_rust_wasm"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[lib]
+crate-type = ['cdylib']
+
+[dependencies]
+

__wasm/wasmtime/wasms/simple_rust_wasm/justfile

@@ -0,0 +1,7 @@
+_:
+  @just --list
+
+build:
+  cargo build --target wasm32-unknown-unknown
+
+

__wasm/wasmtime/wasms/simple_rust_wasm/src/lib.rs

@@ -0,0 +1,12 @@
+#[link(wasm_import_module = "host")]
+extern "C" {
+
+     #[link_name = "hello"]
+    fn host_hello(a: i32);
+}
+
+#[no_mangle]
+pub extern "C" fn hello() {
+  unsafe { host_hello(3); }
+}
+