ww build: honor Go output permission modes

selfhost/cmd/w6l/main.ww

@@ -302,8 +302,10 @@ export fn main(argc: i32, argv: **u8) i32 = {
 		return 1;
 	};
 
+	// Pinned Go's BuildInstallFunc creates an ordinary linked command with
+	// 0o777; open applies the invoking process's umask to this fresh stage.
 	let flags: os.flag = os.flag.WRONLY | os.flag.CREATE | os.flag.TRUNC;
-	let fd: i32 = os.open(pathstr(outpath), flags, 493i32);	// 0o755
+	let fd: i32 = os.open(pathstr(outpath), flags, 511i32);	// 0o777
 	if (fd < 0) {
 		let m: str = "w6l: cannot open output\n";
 		os.write(2, m.ptr, m.len: u64);