authfs: add readers for chunked data

This change adds simple readers to read fixed size chunks from file and
memory. Also set up basic build rules and test rules.

The reader will be used by later fs-verity implementation to read and
verify each 4K block access of a file.

Bug: 171310075
Test: atest authfs_host_test_src_lib

Change-Id: I194cf431d4aa6dd49cc19aea65d233ccdc6c5452
4 files changed
tree: 88d967ae361726461ff8d705b351ecc342894f7d
  1. authfs/
  2. docs/
  3. .clang-format
  4. PREUPLOAD.cfg