Verified Boot (AVB) enable in a product build

I'm studying and using AVB to verify vendor.img, boot.img and system.img. I did the first test using aosp_arm-eng in lunch menu to enable flags like BOARD_AVB_ENABLE and BOARD_AVB_KEY_PATH. As it was a generic build, it had a BoardConfig.mk in /build/target/board/generic to configure this flags.

But now I want to build a product version. I looked for the same BoardConfig.mk file in /build/target/product to change, but it doesn't exist. I found a vboot.mk file that looks like a configuration file for AVB, but every flag there is already enabled and it still doesn't create a vbmeta.img in build process.

So, what's the responsible file to enable the creation of vbmeta.img when I'm using a product build?