Add TARGET_USERIMAGES_USE_EXT4 to mini_mips to fix broken build

Change-Id: I9882fbc685d09fc2e32857270483052f11ab0aa8
diff --git a/BoardConfig.mk b/BoardConfig.mk
index b677b4a..7b81ae0 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -20,3 +20,12 @@
 USE_OPENGL_RENDERER := true
 
 BOARD_USE_LEGACY_UI := true
+
+# PDK does not use ext4 image, but it is added here to prevent build break.
+TARGET_USERIMAGES_USE_EXT4 := true
+BOARD_SYSTEMIMAGE_PARTITION_SIZE := 576716800
+BOARD_USERDATAIMAGE_PARTITION_SIZE := 419430400
+BOARD_CACHEIMAGE_PARTITION_SIZE := 69206016
+BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
+BOARD_FLASH_BLOCK_SIZE := 512
+TARGET_USERIMAGES_SPARSE_EXT_DISABLED := true