Skip tar warnings during backup procedure

when files/folders changed

changelogs/unreleased/litvinov-evgeny-7314-backup-files-skip-warning.yml

+---
+title: Skip warning for file changed during backup instead of failing the backup operation
+merge_request: 40572
+author:
+type: fixed

lib/backup/files.rb

@@ -31,10 +31,10 @@ module Backup
           raise Backup::Error, 'Backup failed'
         end
 
-        run_pipeline!([%W(#{tar} --exclude=lost+found -C #{@backup_files_dir} -cf - .), gzip_cmd], out: [backup_tarball, 'w', 0600])
+        run_pipeline!([%W(#{tar} --warning=no-file-changed --exclude=lost+found -C #{@backup_files_dir} -cf - .), gzip_cmd], out: [backup_tarball, 'w', 0600])
         FileUtils.rm_rf(@backup_files_dir)
       else
-        run_pipeline!([%W(#{tar} --exclude=lost+found -C #{app_files_dir} -cf - .), gzip_cmd], out: [backup_tarball, 'w', 0600])
+        run_pipeline!([%W(#{tar} --warning=no-file-changed --exclude=lost+found -C #{app_files_dir} -cf - .), gzip_cmd], out: [backup_tarball, 'w', 0600])
       end
     end