Enable BOARD_EXT4_SHARE_DUP_BLOCKS to free up space in system/vendor.

Partition   Before      After
system      0           30349312
vendor      13408256    15296512

Bug: 129648823
Test: mount partition images; df
Change-Id: I01005021b3b0d35b1acca98813879d338b8ee4ed
(cherry picked from commit 5df29fb55d9fde5573fd13840df430e536a4eaaf)
diff --git a/sailfish/BoardConfig.mk b/sailfish/BoardConfig.mk
index 73df581..3c90f23 100644
--- a/sailfish/BoardConfig.mk
+++ b/sailfish/BoardConfig.mk
@@ -84,6 +84,7 @@
 BOARD_PERSISTIMAGE_PARTITION_SIZE := 33554432
 BOARD_PERSISTIMAGE_FILE_SYSTEM_TYPE := ext4
 BOARD_FLASH_BLOCK_SIZE := 131072 # (BOARD_KERNEL_PAGESIZE * 64)
+BOARD_EXT4_SHARE_DUP_BLOCKS := true
 
 TARGET_USES_ION := true
 TARGET_USES_NEW_ION_API :=true