Merge libsync_recovery rules into libsync.

Statically linking against libsync is no longer a concern, since libsync
has supported the modern sync ABI (which is frozen upstream) after the
recent cleanup works.

Test: `m dist` with aosp_taimen-userdebug
Change-Id: Ic162bc7ff7c9dd306658d11d4b71e2d18730a2ee