enable BOARD_EXT4_SHARE_DUP_BLOCKS for generic_arm64

Bug: 154907226
Change-Id: Iab55afbfaf7d28ac0e826f8eb94b113a2780a4c9
diff --git a/target/board/generic_arm64/BoardConfig.mk b/target/board/generic_arm64/BoardConfig.mk
index 91d5692..d793c38 100644
--- a/target/board/generic_arm64/BoardConfig.mk
+++ b/target/board/generic_arm64/BoardConfig.mk
@@ -54,6 +54,8 @@
 
 include build/make/target/board/BoardConfigGsiCommon.mk
 
+BOARD_EXT4_SHARE_DUP_BLOCKS := true
+
 TARGET_NO_KERNEL := false
 TARGET_NO_VENDOR_BOOT := true
 BOARD_USES_RECOVERY_AS_BOOT := true