add crosvm to com.android.virt

To do so, crosvm and its dependencies have the apex_available property
set to "//apex_available:platform", "com.android.virt" to explicitly
acknowledge the joining.

Bug: 174639241
Test: m com.android.virt
Change-Id: Id31be39bf7352b73309d64c95d60ffb8c5104036
diff --git a/Android.bp b/Android.bp
index 126d2c0..1db119e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -12,6 +12,10 @@
     proc_macros: [
         "libwire_format_derive",
     ],
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.virt",
+    ],
 }
 
 rust_defaults {