recovery: add --fsck_unshare_blocks option for adb remount

Allow "adb remount" on deduplicated filesystems to reboot into recovery
and run e2fsck to undo deduplication. The e2fsck binary is copied from
the system partition into tmpfs, and the system partition is unmounted
so e2fsck can run safely.

Bug: 64109868
Test: recovery with --fsck_unshare_blocks; adb remount
Change-Id: I7558749b018b58f3c4339e51a95831dbd5be1ae3

Android.mk

@@ -132,6 +132,7 @@ include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := \
     adb_install.cpp \
+    fsck_unshare_blocks.cpp \
     fuse_sdcard_provider.cpp \
     install.cpp \
     recovery.cpp \
@@ -192,6 +193,13 @@ LOCAL_REQUIRED_MODULES += \
 endif
 endif
 
+# e2fsck is needed for adb remount -R.
+ifeq ($(BOARD_EXT4_SHARE_DUP_BLOCKS),true)
+ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
+LOCAL_REQUIRED_MODULES += e2fsck_static
+endif
+endif
+
 ifeq ($(BOARD_CACHEIMAGE_PARTITION_SIZE),)
 LOCAL_REQUIRED_MODULES += \
     recovery-persist \