test a potential modules-related fix for windows test failure

Author: hyp

test/Interop/SwiftToCxxToSwift/hide-swift-module-namespace-in-swift.swift

@@ -6,7 +6,7 @@
 
 // RUN: %FileCheck %s < %t/swiftMod.h
 
-// RUN: %target-swift-frontend -typecheck %t/swiftMod.swift -typecheck -module-name SwiftMod -emit-clang-header-path %t/swiftMod2.h -I %t -enable-experimental-cxx-interop
+// RUN: %target-swift-frontend -typecheck %t/swiftMod.swift -typecheck -module-name SwiftMod -emit-clang-header-path %t/swiftMod2.h -I %t -enable-experimental-cxx-interop -Xcc -DTEST_FORCE_MODULE_REBUILD
 
 // RUN: %check-interop-cxx-header-in-clang(%t/swiftMod2.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY  -Wno-error)