Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/src/fs/remove_dir.rs

@@ -0,0 +1,12 @@
+use crate::fs::asyncify;
+
+use std::io;
+use std::path::Path;
+
+/// Removes an existing, empty directory.
+///
+/// This is an async version of [`std::fs::remove_dir`](std::fs::remove_dir)
+pub async fn remove_dir(path: impl AsRef<Path>) -> io::Result<()> {
+    let path = path.as_ref().to_owned();
+    asyncify(move || std::fs::remove_dir(path)).await
+}