Skeleton for IVmTethering service with flag guarding

This reverts commit f9676878292a49caa03e5270c3be2769b029db60.

Bug: 340376953
Test: adb shell /apex/com.android.virt/bin/vm run-microdroid --network-supported

Change-Id: I9c859dd43e7ba7c852a71afce8f36ca10477ad24
diff --git a/apex/product_packages.mk b/apex/product_packages.mk
index a318817..486334c 100644
--- a/apex/product_packages.mk
+++ b/apex/product_packages.mk
@@ -56,3 +56,9 @@
     $(error RELEASE_AVF_ENABLE_DICE_CHANGES must also be enabled)
   endif
 endif
+
+ifdef RELEASE_AVF_ENABLE_NETWORK
+  ifndef RELEASE_AVF_ENABLE_LLPVM_CHANGES
+    $(error RELEASE_AVF_ENABLE_LLPVM_CHANGES must also be enabled)
+  endif
+endif