buildman: Make -I the default

At present buildman defaults to running 'mrproper' on every thread before
it starts building commits for each board. This can add a delay of about 5
seconds to the start of the process, since the tools and other invariants
must be rebuilt.

In particular, a build without '-b', to build current source, runs much
slower without -I, since any existing build is removed, thus losing the
possibility of an incremental build.

Partly this behaviour was to avoid strange build-system problems caused by
running 'make defconfig' for one board and then one with a different
architecture. But these problems were fixed quite a while ago.

The -I option (which disabled mrproper) was introduced four years ago and
does not seem to cause any problems with builds.

So make -I the default and deprecate the option. To allow use of
'mrproper', add a new -m flag.

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

tools/buildman/builder.py

@@ -231,7 +231,7 @@ class Builder:
     def __init__(self, toolchains, base_dir, git_dir, num_threads, num_jobs,
                  gnu_make='make', checkout=True, show_unknown=True, step=1,
                  no_subdirs=False, full_path=False, verbose_build=False,
-                 incremental=False, per_board_out_dir=False,
+                 mrproper=False, per_board_out_dir=False,
                  config_only=False, squash_config_y=False,
                  warnings_as_errors=False, work_in_output=False):
         """Create a new Builder object
@@ -252,8 +252,7 @@ class Builder:
             full_path: Return the full path in CROSS_COMPILE and don't set
                 PATH
             verbose_build: Run build with V=1 and don't use 'make -s'
-            incremental: Always perform incremental builds; don't run make
-                mrproper when configuring
+            mrproper: Always run 'make mrproper' when configuring
             per_board_out_dir: Build in a separate persistent directory per
                 board rather than a thread-specific directory
             config_only: Only configure each build, don't build it
@@ -311,7 +310,7 @@ class Builder:
         self.queue = queue.Queue()
         self.out_queue = queue.Queue()
         for i in range(self.num_threads):
-            t = builderthread.BuilderThread(self, i, incremental,
+            t = builderthread.BuilderThread(self, i, mrproper,
                     per_board_out_dir)
             t.setDaemon(True)
             t.start()