fix(xtask): install worker-build when cargo xtask dev needs it

docs/development.md

@@ -11,6 +11,11 @@ subscription, Cloudflare account or GitHub App.
   wrangler). The web app depends on
   [@hyperstructure/design](https://github.com/hyperstructure/design) through
   git, so `npm ci` needs read access to that repository while it is private.
+- [worker-build](https://crates.io/crates/worker-build), which builds the
+  control plane for wrangler. The first `cargo xtask dev` installs it with
+  `cargo install` if it isn't on your PATH. On Linux that needs pkg-config
+  and OpenSSL's headers: `sudo apt install pkg-config libssl-dev` on Debian
+  and Ubuntu.
 - Optional, for release builds: [zig](https://ziglang.org) and
   `cargo install cargo-zigbuild`.
 

xtask/src/dev.rs

@@ -46,6 +46,9 @@ pub fn dev(root: &Path, opts: DevOpts) -> Result<()> {
     if !root.join("node_modules").exists() {
         util::npm_install(root)?;
     }
+    // wrangler dev builds the Worker with `worker-build --dev` (wrangler.toml):
+    // this installs it when it is missing.
+    util::worker_build()?;
     dev_vars(root)?;
     run(Command::new("cargo")
         .args([