cmake: Use tar.xz source package generator

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

CPackConfig.cmake

@@ -18,7 +18,7 @@ set(CPACK_PACKAGE_VERSION "${CPACK_PACKAGE_VERSION_MAJOR}.${CPACK_PACKAGE_VERSIO
 
 
 ### source generator
-set(CPACK_SOURCE_GENERATOR "TGZ")
+set(CPACK_SOURCE_GENERATOR "TXZ")
 set(CPACK_SOURCE_IGNORE_FILES "~$;[.]swp$;/[.]svn/;/[.]git/;.gitignore;/build/;/obj/;tags;cscope.*")
 set(CPACK_SOURCE_PACKAGE_FILE_NAME "${CPACK_PACKAGE_NAME}-${CPACK_PACKAGE_VERSION}")