adding to the package-template dir

package-templates/rust/build.rs

@@ -0,0 +1,28 @@
+use std::fs;
+use std::io::Path;
+use std::io::Write;
+
+use std::process::Command;
+
+fn main() {
+    if !Path::new("./ui").exists() {
+        // no UI to build
+        return;
+    }
+    // Touch a marker file to ensure that cargo reruns this build script no matter what
+    // unless it may decide in appropriately that it doesn't need to run the script.
+    fs::File::create("./ui_build")
+        .unwrap()
+        .write_all(b"")
+        .unwrap();
+
+    Command::new("yarn")
+        .current_dir("./ui")
+        .status()
+        .expect("Failed to run `yarn`");
+    Command::new("yarn")
+        .args(&["build"])
+        .current_dir("./ui")
+        .status()
+        .expect("Failed to run build project");
+}