Mangle the open_FILE symbols to avoid conflict with open_file:
Warning: public '_archive_read_open_file'
in module 'archive_read_open_filename.c' clashes with
prior module 'archive_read_open_file.c'
Warning: public '_archive_write_open_file'
in module 'archive_write_open_filename.c' clashes with
prior module 'archive_write_open_file.c'
This workaround should not go upstream because it will break when
mixing compilers.
b5dd9aa482