Added test.

Author: David Ungar

test/Frontend/batch_mode_module_file_names_as_main_output.swift

@@ -0,0 +1,6 @@
+// RUN: %empty-directory(%t)
+// RUN: touch %t/file-01.swift
+// RUN: touch %t/file-02.swift
+// RUN: cd %t
+// RUN: %target-swift-frontend -emit-module -primary-file file-01.swift -primary-file file-02.swift -o file-01.swiftmodule -o file-02.swiftmodule -module-name foo
+// RUN: test -e file-01.swiftmodule -a -e file-02.swiftmodule