buildman: Allow adjusting board config on the fly

Add a -a option to specify changes to the config before the build
commences. For example

   buildman -a ~CONFIG_CMDLINE

disables CONFIG_CMDLINE before doing the build.

This makes it easier to try things out as well as to write tests without
creating a new board or manually manging the .config file.

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

tools/buildman/cmdline.py

@@ -13,6 +13,8 @@ def ParseArgs():
             args: command lin arguments
     """
     parser = OptionParser()
+    parser.add_option('-a', '--adjust-cfg', type=str, action='append',
+          help='Adjust the Kconfig settings in .config before building')
     parser.add_option('-A', '--print-prefix', action='store_true',
           help='Print the tool-chain prefix for a board (CROSS_COMPILE=)')
     parser.add_option('-b', '--branch', type='string',