buildman: Add support for environment delta in summary

When summarising the builds, add the -U option to emit delta lines for
the default environment built into U-Boot at each commit.

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 4ac4386..bc08197 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -319,7 +319,8 @@
         builder.SetDisplayOptions(options.show_errors, options.show_sizes,
                                   options.show_detail, options.show_bloat,
                                   options.list_error_boards,
-                                  options.show_config)
+                                  options.show_config,
+                                  options.show_environment)
         if options.summary:
             builder.ShowSummary(commits, board_selected)
         else: