[source] target/imagebuilder: Switch to xz compression instead of bz2

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/636a069c42b4c98e52fea949961cceccb8273b1f

commit 636a069c42b4c98e52fea949961cceccb8273b1f
Author: Daniel Engberg <diizzyy at users.noreply.github.com>
AuthorDate: Tue Oct 11 14:14:48 2016 +0200

    target/imagebuilder: Switch to xz compression instead of bz2
    
    Switch to xz compression instead of using bz2.
    Saves about 20% of total size (ar71xx)
    
    Signed-off-by: Daniel Engberg <daniel.engberg.lists at pyret.net>
---
 target/imagebuilder/Makefile | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/target/imagebuilder/Makefile b/target/imagebuilder/Makefile
index b809193..b43662b 100644
--- a/target/imagebuilder/Makefile
+++ b/target/imagebuilder/Makefile
@@ -21,7 +21,7 @@ IB_DTSDIR:=$(patsubst $(TOPDIR)/%,$(PKG_BUILD_DIR)/%,$(LINUX_DIR))/arch/$(ARCH)/
 
 all: compile
 
-$(BIN_DIR)/$(IB_NAME).tar.bz2: clean
+$(BIN_DIR)/$(IB_NAME).tar.xz: clean
 	rm -rf $(PKG_BUILD_DIR)
 	mkdir -p $(IB_KDIR) $(IB_LDIR) $(PKG_BUILD_DIR)/staging_dir/host/lib \
 		$(PKG_BUILD_DIR)/target $(PKG_BUILD_DIR)/scripts $(IB_DTSDIR)
@@ -77,12 +77,12 @@ endif
 	find $(STAGING_DIR_HOST)/bin -maxdepth 1 -type f -perm -u=x \
 	  | $(XARGS) $(SCRIPT_DIR)/bundle-libraries.sh $(PKG_BUILD_DIR)/staging_dir/host/bin/
 	STRIP=sstrip $(SCRIPT_DIR)/rstrip.sh $(PKG_BUILD_DIR)/staging_dir/host/bin/
-	$(TAR) -cf - -C $(BUILD_DIR) $(IB_NAME) | bzip2 -c > $@
+	$(TAR) -cf - -C $(BUILD_DIR) $(IB_NAME) | xz -zc -7e > $@
 
 download:
 prepare:
-compile: $(BIN_DIR)/$(IB_NAME).tar.bz2
+compile: $(BIN_DIR)/$(IB_NAME).tar.xz
 install: compile
 
 clean: FORCE
-	rm -rf $(PKG_BUILD_DIR) $(BIN_DIR)/$(IB_NAME).tar.bz2
+	rm -rf $(PKG_BUILD_DIR) $(BIN_DIR)/$(IB_NAME).tar.xz