buildman: Allow comparison of build configuration

It is useful to be able to see CONFIG changes made by commits. Add this
feature to buildman using the -K flag so that all CONFIG changes are
reported.

The CONFIG options exist in a number of files. Each is reported
individually as well as a summary that covers all files. The output
shows three parts: green for additions, red for removals and yellow for
changes.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 720b978..8b3cd30 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -282,7 +282,8 @@
             options.show_detail = True
         builder.SetDisplayOptions(options.show_errors, options.show_sizes,
                                   options.show_detail, options.show_bloat,
-                                  options.list_error_boards)
+                                  options.list_error_boards,
+                                  options.show_config)
         if options.summary:
             builder.ShowSummary(commits, board_selected)
         else: