stdlib: enable CxxStdlib module on Windows

Enable this module on Windows for enabling C++ Interop.

Author: compnerd

stdlib/public/Cxx/std/CMakeLists.txt

@@ -31,7 +31,7 @@ add_swift_target_library(swiftCxxStdlib STATIC NO_LINK_NAME IS_STDLIB IS_SWIFT_O
     ${SWIFT_SDK_LINUX_CXX_OVERLAY_SWIFT_COMPILE_FLAGS}
 
     LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
-    TARGET_SDKS ALL_APPLE_PLATFORMS LINUX
+    TARGET_SDKS ALL_APPLE_PLATFORMS LINUX WINDOWS
     INSTALL_IN_COMPONENT compiler
     INSTALL_WITH_SHARED
     DEPENDS libstdcxx-modulemap libcxxshim_modulemap)