run v with -N -W flags in build_examples.vsh, to find deprecation problems earlier

Author: spytheman

examples/build_examples.vsh

@@ -31,7 +31,7 @@ mut err := 0
 mut failures := []string{}
 chdir(examples_dir)!
 for entry_idx, entry in entries {
-	cmd := 'v ${entry}'
+	cmd := 'v -N -W ${entry}'
 	println_one_of_many('compile with: ${cmd}', entry_idx, entries.len)
 	ret := execute(cmd)
 	if ret.exit_code != 0 {