Add vendor_available: true to Android.bp.

Bug: 78570710
Test: Still builds.
Change-Id: If6568af38e8648a80e6e57fac5c34577e9bb48d8
diff --git a/Android.bp b/Android.bp
index 39e7ebb..923cb10 100644
--- a/Android.bp
+++ b/Android.bp
@@ -22,6 +22,7 @@
 
 cc_library_static {
     name: "libffi",
+    vendor_available: true,
     cflags: [
         "-Wall",
         "-Werror",