buildman: Tidy up the 'cloning' message

On a machine with a lot of CPUs this prints a lot of useless lines of the
form:

   Cloning repo for thread <n>

Adjust the output so that these all appear on one line, and disappear when
the cloning is complete.

Note: This cloning is actually unnecessary and very wasteful on disk space
(about 3.5GB each time). It would be better to create symlinks.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/buildman/builder.py

@@ -1366,8 +1366,10 @@ class Builder:
             if os.path.exists(git_dir):
                 gitutil.Fetch(git_dir, thread_dir)
             else:
-                Print('Cloning repo for thread %d' % thread_num)
+                Print('\rCloning repo for thread %d' % thread_num,
+                      newline=False)
                 gitutil.Clone(src_dir, thread_dir)
+                Print('\r%s\r' % (' ' * 30), newline=False)
 
     def _PrepareWorkingSpace(self, max_threads, setup_git):
         """Prepare the working directory for use.