Add support for checkpointing

Checkpointing uses a combination of files on the meta partition
and the checkpoint= fs_mgr flag. Checkpointed partitions will
revert to their starting state on reboot unless checkpoint commit
is called.

Test: Run vdc commands, check file on metadata
Merged-In: Icba16578608a6cbf922472e9d4ae5b8cf5f016c6
Change-Id: Icba16578608a6cbf922472e9d4ae5b8cf5f016c6
diff --git a/Android.bp b/Android.bp
index 8fd29f0..1e45727 100644
--- a/Android.bp
+++ b/Android.bp
@@ -95,6 +95,7 @@
     srcs: [
         "Benchmark.cpp",
         "CheckEncryption.cpp",
+        "Checkpoint.cpp",
         "Devmapper.cpp",
         "EncryptInplace.cpp",
         "Ext4Crypt.cpp",