initial buildroot for linux 5.15

fs/erofs/Config.in

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+config BR2_TARGET_ROOTFS_EROFS
+	bool "erofs root filesystem"
+	select BR2_PACKAGE_HOST_EROFS_UTILS
+	help
+	  Build a EROFS root filesystem.
+
+if BR2_TARGET_ROOTFS_EROFS
+
+config BR2_TARGET_ROOTFS_EROFS_LZ4HC
+	bool "lz4hc compression"
+	help
+	  Use lz4 high-compression to compress data in the filesystem.
+
+config BR2_TARGET_ROOTFS_EROFS_PCLUSTERSIZE
+	int "pcluster size"
+	default 0
+	help
+	  Specify the maximum size of physical cluster in bytes, as a
+	  multiple of 4KiB, for the big pcluster feature in order to
+	  get much better compression ratios (thus better sequential
+	  read performance for common storage devices), which has been
+	  introduced since Linux 5.13.
+
+endif # BR2_TARGET_ROOTFS_EROFS

fs/erofs/erofs.mk

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+################################################################################
+#
+# Build the EROFS root filesystem image
+#
+################################################################################
+
+ROOTFS_EROFS_DEPENDENCIES = host-erofs-utils
+
+ifeq ($(BR2_TARGET_ROOTFS_EROFS_LZ4HC),y)
+ROOTFS_EROFS_ARGS += -zlz4hc
+endif
+
+ifneq ($(BR2_TARGET_ROOTFS_EROFS_PCLUSTERSIZE),0)
+ROOTFS_EROFS_ARGS += -C$(strip $(BR2_TARGET_ROOTFS_EROFS_PCLUSTERSIZE))
+endif
+
+define ROOTFS_EROFS_CMD
+	$(HOST_DIR)/bin/mkfs.erofs $(ROOTFS_EROFS_ARGS) $@ $(TARGET_DIR)
+endef
+
+$(eval $(rootfs))