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

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

Change-Id: I11453cd2c418cf8b1af57e482e68f1489afde2e4
Signed-off-by: Automerger Merge Worker <[email protected]>