buildman: Use oldconfig when adjusting the config

We cannot be sure that the new config is consistent, particularly when
changing a major item like CONFIG_CMDLINE. Use 'make oldconfig' to
check that and avoid any such problems.

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

tools/buildman/builderthread.py

@@ -426,6 +426,12 @@ class BuilderThread(threading.Thread):
 
         # Now do the build, if everything looks OK
         if result.return_code == 0:
+            if adjust_cfg:
+                oldc_args = list(args) + ['oldconfig']
+                oldc_result = self.make(commit, brd, 'oldconfig', cwd,
+                                        *oldc_args, env=env)
+                if oldc_result.return_code:
+                    return oldc_result
             result = self._build(commit, brd, cwd, args, env, cmd_list,
                                  config_only)
             if adjust_cfg: