project: fix variable typo

Bug: https://crbug.com/gerrit/11293
Reported-by: Daniel Kutik <daniel.kutik@lavawerk.com>
Change-Id: I37bac58aa1dc9ecc10e29253d14ff9e6fb42427c
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/298942
Reviewed-by: Ian Kasprzak <iankaz@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

project.py

@@ -1150,7 +1150,7 @@ class Project(object):
         p = GitCommand(self, cmd, bare=True, capture_stdout=bool(output_redir),
                        merge_output=bool(output_redir))
         if p.stdout and output_redir:
-          buf.write(p.stdout)
+          output_redir.write(p.stdout)
         if p.Wait() != 0:
           return False
         platform_utils.remove(alternates_file)