Enable verified boot for microdroid

Bug: 181923506
Test: atest MicrodroidHostTestCases
crosvm: U-Boot 2021.01-07985-g67ec634914 (Mar 25 2021 - 16:16:08 +0000)
crosvm:
crosvm: DRAM:  256 MiB
crosvm: Loading Environment from Raw Disk... OK
crosvm: Hit any key to stop autoboot:  0
crosvm: ## Android Verified Boot 2.0 version 1.1.0
crosvm: read_is_device_unlocked not supported yet
crosvm: read_rollback_index not supported yet
crosvm: read_rollback_index not supported yet
crosvm: read_rollback_index not supported yet
crosvm: read_is_device_unlocked not supported yet
crosvm: Verification passed successfully
crosvm: ANDROID: reboot reason: "(none)"

Change-Id: I6b0cca80d00351f6e0062541818971e761f1b67b
diff --git a/microdroid/uboot-env-x86_64.txt b/microdroid/uboot-env-x86_64.txt
index ab0fc26..ffc0462 100644
--- a/microdroid/uboot-env-x86_64.txt
+++ b/microdroid/uboot-env-x86_64.txt
@@ -1,7 +1,7 @@
 # Static u-boot environment variables for microdroid. See b/180481192
 
 # Boot the device following the Android boot procedure
-bootcmd=boot_android virtio 0#misc
+bootcmd=avb init virtio 0 && avb verify _a && boot_android virtio 0#misc
 
 bootdelay=0
 
diff --git a/microdroid/uboot-env.txt b/microdroid/uboot-env.txt
index b7940e5..0bdc591 100644
--- a/microdroid/uboot-env.txt
+++ b/microdroid/uboot-env.txt
@@ -1,7 +1,7 @@
 # Static u-boot environment variables for microdroid. See b/180481192
 
 # Boot the device following the Android boot procedure
-bootcmd=boot_android virtio 0#misc
+bootcmd=avb init virtio 0 && avb verify _a && boot_android virtio 0#misc
 
 bootdelay=0
 fdtaddr=0x80000000