link in the prelude object

boot1/build.rs

@@ -20,24 +20,31 @@ fn main() {
 }
 
 fn emit_link_args() {
-  println!("cargo::rustc-link-arg=-Tlink.ld");
+  let linker_script_path = "link.ld";
+  println!("cargo::rustc-link-arg=-T{}", linker_script_path);
+  rerun_if_changed(linker_script_path.as_ref());
 }
 
 fn rerun_if_changed(path: &Path) {
-  if let Some(path_str) = path.to_str() {
-    println!("cargo::rerun-if-changed={}", path_str);
-  }
-  else {
-    eprintln!("invalid unicode file path");
-  }
+  let path_str = path.to_str()
+    .expect("expected path to be valid utf8");
+  println!("cargo::rerun-if-changed={}", path_str);
+}
+
+fn link_obj(path: &Path) {
+  let path_str = path.to_str()
+    .expect("expected path to be valid utf8");
+  println!("cargo::rustc-link-arg={}", path_str);
 }
 
 fn build_asm(nasm: &Nasm, out_dir: &Path) {
+  let prelude_obj_path = out_dir.join("prelude.o");
   nasm.assemble(
-    &out_dir.join("prelude.bin"),
+    &prelude_obj_path,
     &["asm/prelude.s".as_ref()],
     &["../include".as_ref()],
   ).unwrap();
+  link_obj(&prelude_obj_path);
 }
 
 struct Nasm {
@@ -57,9 +64,9 @@ impl Nasm {
 
     let mut cmd = Command::new(&self.bin_path);
     cmd
+      .arg("-Werror")
       .arg("-f")
-      .arg("bin")
-      .arg("-Werror");
+      .arg("elf");
 
     for include in includes {
       let mut buf = OsString::new();