unbreak sdk_phone_x86 boot

Bug: 146580512
Test: choosecombo 1 sdk_phone_x86 userdebug; m; emulator
Change-Id: I8227291c89e1cafc35e63eccd2f5ca34ecbd5434
diff --git a/target/product/sdk_phone_x86.mk b/target/product/sdk_phone_x86.mk
index 9df26a9..4f7602d 100644
--- a/target/product/sdk_phone_x86.mk
+++ b/target/product/sdk_phone_x86.mk
@@ -15,6 +15,7 @@
 #
 QEMU_USE_SYSTEM_EXT_PARTITIONS := true
 PRODUCT_USE_DYNAMIC_PARTITIONS := true
+BOARD_AVB_MAKE_VBMETA_IMAGE_ARGS += --flags 2
 
 #
 # All components inherited here go to system image