Build: Update Mips64 generic build for ART

For ART testing, we need:

1) A larger userdata partition. A lot of files end up there as it
is multi-arch.

2) Don't strip prebuilts. Technically we only care about core-libart,
but this is the best high-level change that doesn't impact other
files.

Change-Id: Ic36bfcf80ba50a602752ca0a3031dda89a0f3051
diff --git a/target/board/generic_mips64/BoardConfig.mk b/target/board/generic_mips64/BoardConfig.mk
index 5c13447..8e8a68b 100644
--- a/target/board/generic_mips64/BoardConfig.mk
+++ b/target/board/generic_mips64/BoardConfig.mk
@@ -66,10 +66,12 @@
 
 TARGET_USERIMAGES_USE_EXT4 := true
 BOARD_SYSTEMIMAGE_PARTITION_SIZE := 1342177280  # 1.25 GB swag, 20% more than before
-BOARD_USERDATAIMAGE_PARTITION_SIZE := 734003200
+BOARD_USERDATAIMAGE_PARTITION_SIZE := 1610612736  # 1.5 GB, lots of space for running tests
 BOARD_CACHEIMAGE_PARTITION_SIZE := 69206016
 BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
 BOARD_FLASH_BLOCK_SIZE := 512
 TARGET_USERIMAGES_SPARSE_EXT_DISABLED := true
 
 BOARD_SEPOLICY_DIRS += build/target/board/generic/sepolicy
+
+DEX_PREOPT_DEFAULT := nostripping