Add PRODUCT_AVF_KERNEL_MODULES_ENABLED

This flag controls whether com.android.virt APEX should include an
additional kernel image that supports modules loading.

Bug: 283822676
Bug: 278008256
Test: m
Change-Id: I296c57308e130ee6d5d185dcb4b690d11d2b04ac
diff --git a/core/product.mk b/core/product.mk
index 818aac2..6f54b78 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -389,6 +389,9 @@
 # If true, installs a full version of com.android.virt APEX.
 _product_single_value_vars += PRODUCT_AVF_ENABLED
 
+# If true, kernel with modules will be used for Microdroid VMs.
+_product_single_value_vars += PRODUCT_AVF_KERNEL_MODULES_ENABLED
+
 # List of .json files to be merged/compiled into vendor/etc/linker.config.pb
 _product_list_vars += PRODUCT_VENDOR_LINKER_CONFIG_FRAGMENTS