Add microdroid_vbmeta_bootconfig to arm64

This fixes the following error when starting a VM on arm64 devices:

Status(-8, EX_SERVICE_SPECIFIC): '-1: Failed to load app config from
assets/vm_config.json: Failed to open
"/apex/com.android.virt/etc/fs/microdroid_vbmeta_bootconfig.img"'

Bug: 203031847
Test: able to boot microdroid on an arm64 device
Change-Id: I3c9a8654ec19496bbe538f5838f84a0dde80955f
diff --git a/apex/Android.bp b/apex/Android.bp
index 88487e4..24a2a8e 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -27,6 +27,7 @@
                 "microdroid_boot-5.10",
                 "microdroid_vendor_boot-5.10",
                 "microdroid_vbmeta",
+                "microdroid_vbmeta_bootconfig",
             ],
         },
         x86_64: {