Makefile: "make dist" generates a .xz, not .bz2

Fixes: 9bc9e95119 (make-release: switch to .xz format by default)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
(cherry picked from commit 14fb6dbbc5)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

Makefile

@@ -213,10 +213,10 @@ clean: recurse-clean
 
 VERSION = $(shell cat $(SRC_PATH)/VERSION)
 
-dist: qemu-$(VERSION).tar.bz2
+dist: qemu-$(VERSION).tar.xz
 
-qemu-%.tar.bz2:
-	$(SRC_PATH)/scripts/make-release "$(SRC_PATH)" "$(patsubst qemu-%.tar.bz2,%,$@)"
+qemu-%.tar.xz:
+	$(SRC_PATH)/scripts/make-release "$(SRC_PATH)" "$(patsubst qemu-%.tar.xz,%,$@)"
 
 distclean: clean recurse-distclean
 	-$(quiet-@)test -f build.ninja && $(NINJA) $(NINJAFLAGS) -t clean -g || :