Allow the ART module to use "libc++fs". am: 978cfa2e7a am: 58e61553fa am: 8dbeb2515c

Original change: https://android-review.googlesource.com/c/platform/external/libcxx/+/1890116

Change-Id: I846323ebb6274a7bbfab8c0601261cdb4b9cf1f0