Remove potentially expensive filter if argument list is long

Author: cltnschlosser

Sources/SwiftDriver/Driver/Driver.swift

@@ -508,18 +508,21 @@ extension Driver {
         continue
       } else if char.isWhitespace && !quoted {
         // This is unquoted, unescaped whitespace, start a new token.
-        tokens.append(token)
-        token = ""
+        if !token.isEmpty {
+          tokens.append(token)
+          token = ""
+        }
         continue
       }
 
       token.append(char)
     }
     // Add the final token
-    tokens.append(token)
+    if !token.isEmpty {
+      tokens.append(token)
+    }
 
-    // Filter any empty tokens that might be parsed if there's excessive whitespace.
-    return tokens.filter { !$0.isEmpty }
+    return tokens
   }
 
   /// Tokenize each line of the response file, omitting empty lines.