build.rs: Restrict preassembly to nasm to simplify logic.

Call `nasm` directly during preassembly. This leaves one caller each of
`compile()` and `new_build()`. Inline them into their single caller.

build.rs

@@ -387,9 +387,8 @@ fn pregenerate_asm_main() {
                 force_warnings_into_errors: true,
             };
 
-            let mut b = new_build(&target, &pregenerated_tmp);
             for src in srcs {
-                compile(&mut b, &src, &target, &pregenerated_tmp, &pregenerated);
+                nasm(&src, &target.arch, &pregenerated_tmp, &pregenerated);
             }
         }
     }
@@ -486,24 +485,24 @@ fn build_c_code(
     );
 }
 
-fn new_build(target: &Target, include_dir: &Path) -> cc::Build {
-    let mut b = cc::Build::new();
-    configure_cc(&mut b, target, include_dir);
-    b
-}
-
 fn build_library<'a>(
     target: &Target,
     out_dir: &Path,
     lib_name: &str,
     srcs: impl Iterator<Item = &'a PathBuf>,
     preassembled_objs: &[PathBuf],
 ) {
-    let mut c = new_build(target, out_dir);
+    let mut c = cc::Build::new();
+    configure_cc(&mut c, target, out_dir);
 
     // Compile all the (dirty) source files into object files.
     srcs.for_each(|src| {
-        compile(&mut c, src, target, out_dir, out_dir);
+        if !matches!(src.extension(), Some(e) if e == "asm") {
+            let _ = c.file(src);
+        } else {
+            let obj = nasm(src, &target.arch, out_dir, out_dir);
+            let _ = c.object(obj);
+        }
     });
 
     preassembled_objs.iter().for_each(|obj| {
@@ -538,15 +537,6 @@ fn build_library<'a>(
     println!("cargo:rustc-link-lib=static={}", lib_name);
 }
 
-fn compile(b: &mut cc::Build, p: &Path, target: &Target, include_dir: &Path, out_dir: &Path) {
-    if !matches!(p.extension(), Some(e) if e == "asm") {
-        let _ = b.file(p);
-    } else {
-        let obj = nasm(p, &target.arch, include_dir, out_dir);
-        let _ = b.object(obj);
-    }
-}
-
 fn obj_path(out_dir: &Path, src: &Path) -> PathBuf {
     let mut out_path = out_dir.join(src.file_name().unwrap());
     // To eliminate unnecessary conditional logic, use ".o" as the extension,