[Function builders] Update test case

Author: DougGregor

test/ModuleInterface/function_builders.swift

@@ -26,7 +26,15 @@ public struct TupleBuilder {
     return (t1, t2, t3, t4, t5)
   }
 
-  public static func buildDo<T>(_ value: T) -> T { return value }
+  public static func buildDo<T1, T2>(_ t1: T1, _ t2: T2) -> (T1, T2) {
+    return (t1, t2)
+  }
+
+  public static func buildDo<T1, T2, T3>(_ t1: T1, _ t2: T2, _ t3: T3)
+      -> (T1, T2, T3) {
+    return (t1, t2, t3)
+  }
+
   public static func buildIf<T>(_ value: T?) -> T? { return value }
 }