Add microdroid to the virt APEX

Bug: 177630284
Test: m com.android.virt
Change-Id: I2a5af04287dc94db028c4aaccfeeb0fc7734993e
diff --git a/apex/Android.bp b/apex/Android.bp
index 06d56f2..ef4c0f5 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -23,6 +23,7 @@
         },
     },
     binaries: ["assemble_cvd"],
+    filesystems: ["microdroid"],
 }
 
 apex_key {