buildman: Add a flag to force mrproper on failure

When a file is removed by a commit (e.g. include/common.h yay!) it can
cause incremental build failures since one of the dependency files from
a previous build may mention the file.

Add an option to run 'make mrproper' automatically when a build fails.
This can be used to automatically resolve the problem, without always
adding the large overhead of 'make mrproper' to every build.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/builderthread.py b/tools/buildman/builderthread.py
index c0b1067..bbe2f6f 100644
--- a/tools/buildman/builderthread.py
+++ b/tools/buildman/builderthread.py
@@ -705,8 +705,10 @@
                     # with a reconfig.
                     if self.builder.force_config_on_failure:
                         result, request_config = self.run_commit(commit_upto,
-                            brd, work_dir, True, self.mrproper, False, True,
-                            False, job.work_in_output, job.adjust_cfg)
+                            brd, work_dir, True,
+                            self.mrproper or self.builder.fallback_mrproper,
+                            False, True, False, job.work_in_output,
+                            job.adjust_cfg)
                         did_config = True
                 if not self.builder.force_reconfig:
                     do_config = request_config