libcutils: make vendor_ramdisk_available.

Test: builds
Bug: 156098440
Change-Id: I663a3839e402a83ebf31b8a680c61f1e269548f6
diff --git a/libsystem/Android.bp b/libsystem/Android.bp
index db61669..12c946c 100644
--- a/libsystem/Android.bp
+++ b/libsystem/Android.bp
@@ -2,6 +2,7 @@
     name: "libsystem_headers",
     vendor_available: true,
     recovery_available: true,
+    vendor_ramdisk_available: true,
     host_supported: true,
     native_bridge_supported: true,
     apex_available: [