feat(tvix/eval): Support builtins.bitOr

Bitwise `or` on integers.

Change-Id: I45b0897331d1a9b6840f9d0feedcf10acc67fcec
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6549
Autosubmit: wpcarro <wpcarro@gmail.com>
Reviewed-by: wpcarro <wpcarro@gmail.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/eval/src/builtins/mod.rs

@@ -108,6 +108,13 @@ fn pure_builtins() -> Vec<Builtin> {
                 })
             })
         }),
+        Builtin::new("bitOr", 2, |args, vm| {
+            force!(vm, &args[0], x, {
+                force!(vm, &args[1], y, {
+                    Ok(Value::Integer(x.as_int()? | y.as_int()?))
+                })
+            })
+        }),
         Builtin::new("catAttrs", 2, |mut args, _| {
             let list = args.pop().unwrap().to_list()?;
             let key = args.pop().unwrap().to_str()?;