apertis-abi-compare: convert xml_new and xml_old in string

to be consistent with other arguments passed to run_abi_checker()

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

tools/apertis-abi-compare

@@ -187,12 +187,12 @@ def abi_checker(lib_names_old, xml_descr_old, my_old_ver, lib_names_new, xml_des
             for xml in xml_descr_new:
                 xml_data = pathlib.Path(xml).read_text()
                 if my_lib in xml_data:
-                    xml_new = xml
+                    xml_new = str(xml)
                     break
             for xml in xml_descr_old:
                 xml_data = pathlib.Path(xml).read_text()
                 if my_lib in xml_data:
-                    xml_old = xml
+                    xml_old = str(xml)
                     break
 
             rac_returncode = run_abi_checker(lib, xml_old, my_old_ver, xml_new, my_new_ver, arch)