Detect .xbps as tarballs.

--- a/src/abg-tools-utils.cc
+++ b/src/abg-tools-utils.cc
@@ -690,7 +690,8 @@
       || string_ends_with(file_path, ".tlz")
       || string_ends_with(file_path, ".tar.Z")
       || string_ends_with(file_path, ".taz")
-      || string_ends_with(file_path, ".tz"))
+      || string_ends_with(file_path, ".tz")
+      || string_ends_with(file_path, ".xbps"))
     return FILE_TYPE_TAR;
 
   ifstream in(file_path.c_str(), ifstream::binary);
