Establish native deterministic codegen framework (#45)

tools/codegen/src/main.rs

@@ -0,0 +1,19 @@
+use libremetaverse_codegen::{regenerate, vendor_inputs, workspace_root};
+use std::path::Path;
+
+fn main() {
+    let arguments: Vec<String> = std::env::args().skip(1).collect();
+    let root = workspace_root();
+    let result = match arguments.as_slice() {
+        [command] if command == "generate" => regenerate(&root, false),
+        [command] if command == "check" => regenerate(&root, true),
+        [command, reference] if command == "vendor" => vendor_inputs(&root, Path::new(reference)),
+        _ => Err(
+            "usage: libremetaverse-codegen <generate|check|vendor REFERENCE_CHECKOUT>".to_owned(),
+        ),
+    };
+    if let Err(error) = result {
+        eprintln!("{error}");
+        std::process::exit(2);
+    }
+}