Mark libsync as LL-NDK

libsync is used both by platform (e.g. libui.so) and by same-process
HALs (e.g. android.hardware.graphics.mapper@2.0-impl.so). Therefore it
is eligible for either VNDK-SP or LL-NDK. Among the two choices, LL-NDK
was selected because it is already an NDK and is just a thin wrapper
around a few kernel ioctls.

However, since libui (which is a vendor_available:true library) is using
more symbols that are not available to NDK clients, the extra symbols
are exposed as # vndk tag so that they are only available to VNDK
clients, but not to NDK clients.

Bug: 63866913
Test: BOARD_VNDK_VERSION=current m -j successful (2017 pixel)
Test: the built image is bootable
Change-Id: I60f883c049bd9b4562e6ce34d34ead47ba28af5f

libsync/Android.bp

@@ -22,13 +22,15 @@ cc_defaults {
 
 cc_library_shared {
     name: "libsync",
-    vendor_available: true,
-    vndk: {
-        enabled: true,
-    },
     defaults: ["libsync_defaults"],
 }
 
+llndk_library {
+    name: "libsync",
+    symbol_file: "libsync.map.txt",
+    export_include_dirs: ["include"],
+}
+
 // libsync_recovery is only intended for the recovery binary.
 // Future versions of the kernel WILL require an updated libsync, and will break
 // anything statically linked against the current libsync.

libsync/libsync.map.txt

@@ -19,14 +19,10 @@ LIBSYNC {
     sync_merge; # introduced=26
     sync_file_info; # introduced=26
     sync_file_info_free; # introduced=26
+    sync_wait; # vndk
+    sync_fence_info; # vndk
+    sync_pt_info; # vndk
+    sync_fence_info_free; # vndk
   local:
     *;
 };
-
-LIBSYNC_PLATFORM {
-  global:
-    sync_wait;
-    sync_fence_info;
-    sync_pt_info;
-    sync_fence_info_free;
-} LIBSYNC_PLATFORM;