libc++fs is part of libc++ now. am: e6dbfef4d8

Original change: https://android-review.googlesource.com/c/device/google/felix/+/3122791

Change-Id: I4e10554e6f7abbac2e06953c68bfba6f7ffe77d3
Signed-off-by: Automerger Merge Worker <[email protected]>