Add test for batch mode with -driver-force-response-files.

Author: allevato

test/Driver/force-response-files.swift

@@ -4,3 +4,7 @@
 // RUN: %swiftc_driver -driver-force-response-files -typecheck %S/../Inputs/empty.swift -### 2>&1 | %FileCheck %s
 // CHECK: @
 // CHECK: .resp
+
+// RUN: %swiftc_driver -enable-batch-mode -driver-force-response-files -typecheck %S/../Inputs/empty.swift -### 2>&1 | %FileCheck %s -check-prefix=BATCH
+// BATCH: @
+// BATCH: .resp