libc++fs is part of libc++ now. am: 88e4f8489a am: 7c8c1b4713

Original change: https://android-review.googlesource.com/c/platform/system/gsid/+/3120531

Change-Id: I01675ee63e9334b8512503d962fc69ea349e9a1e
Signed-off-by: Automerger Merge Worker <[email protected]>