Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/process_smoke.rs

@@ -0,0 +1,34 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi cannot run system commands
+
+use tokio::process::Command;
+use tokio_test::assert_ok;
+
+#[tokio::test]
+async fn simple() {
+    let mut cmd;
+
+    if cfg!(windows) {
+        cmd = Command::new("cmd");
+        cmd.arg("/c");
+    } else {
+        cmd = Command::new("sh");
+        cmd.arg("-c");
+    }
+
+    let mut child = cmd.arg("exit 2").spawn().unwrap();
+
+    let id = child.id().expect("missing id");
+    assert!(id > 0);
+
+    let status = assert_ok!(child.wait().await);
+    assert_eq!(status.code(), Some(2));
+
+    // test that the `.wait()` method is fused just like the stdlib
+    let status = assert_ok!(child.wait().await);
+    assert_eq!(status.code(), Some(2));
+
+    // Can't get id after process has exited
+    assert_eq!(child.id(), None);
+    drop(child.kill());
+}