Clarify implementation limitations of funcs in doc comment

src/lib.rs

@@ -3290,6 +3290,9 @@ impl Tool {
         self.args.push(flag);
     }
 
+    /// Checks if an argument or flag has already been specified or conflicts.
+    ///
+    /// Currently only checks optimization flags.
     fn is_duplicate_opt_arg(&self, flag: &OsString) -> bool {
         let flag = flag.to_str().unwrap();
         let mut chars = flag.chars();
@@ -3317,7 +3320,7 @@ impl Tool {
         return false;
     }
 
-    /// Don't push optimization arg if it conflicts with existing args
+    /// Don't push optimization arg if it conflicts with existing args.
     fn push_opt_unless_duplicate(&mut self, flag: OsString) {
         if self.is_duplicate_opt_arg(&flag) {
             println!("Info: Ignoring duplicate arg {:?}", &flag);