buildman: Squash useless output from -K

When using #define CONFIG_SOME_OPTION, the value it set to '1'. When using
defconfig (i.e. CONFIG_SOME_OPTION=y) the value is set to 'y'. This results
in differences showing up with -K. These differences are seldom useful.

Adjust buildman to suppress these differences by default.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/builder.py b/tools/buildman/builder.py
index d834d31..6905ed9 100644
--- a/tools/buildman/builder.py
+++ b/tools/buildman/builder.py
@@ -98,19 +98,22 @@
 # Translate a commit subject into a valid filename
 trans_valid_chars = string.maketrans("/: ", "---")
 
-CONFIG_FILENAMES = [
+BASE_CONFIG_FILENAMES = [
+    'u-boot.cfg', 'u-boot-spl.cfg', 'u-boot-tpl.cfg'
+]
+
+EXTRA_CONFIG_FILENAMES = [
     '.config', '.config-spl', '.config-tpl',
     'autoconf.mk', 'autoconf-spl.mk', 'autoconf-tpl.mk',
     'autoconf.h', 'autoconf-spl.h','autoconf-tpl.h',
-    'u-boot.cfg', 'u-boot-spl.cfg', 'u-boot-tpl.cfg'
 ]
 
 class Config:
     """Holds information about configuration settings for a board."""
-    def __init__(self, target):
+    def __init__(self, config_filename, target):
         self.target = target
         self.config = {}
-        for fname in CONFIG_FILENAMES:
+        for fname in config_filename:
             self.config[fname] = {}
 
     def Add(self, fname, key, value):
@@ -208,7 +211,7 @@
                  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,
-                 config_only=False):
+                 config_only=False, squash_config_y=False):
         """Create a new Builder object
 
         Args:
@@ -232,6 +235,7 @@
             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
+            squash_config_y: Convert CONFIG options with the value 'y' to '1'
         """
         self.toolchains = toolchains
         self.base_dir = base_dir
@@ -260,6 +264,10 @@
         self.full_path = full_path
         self.verbose_build = verbose_build
         self.config_only = config_only
+        self.squash_config_y = squash_config_y
+        self.config_filenames = BASE_CONFIG_FILENAMES
+        if not self.squash_config_y:
+            self.config_filenames += EXTRA_CONFIG_FILENAMES
 
         self.col = terminal.Color()
 
@@ -586,13 +594,15 @@
                             key, value = values
                         else:
                             key = values[0]
-                            value = ''
+                            value = '1' if self.squash_config_y else ''
                         if not key.startswith('CONFIG_'):
                             continue
                     elif not line or line[0] in ['#', '*', '/']:
                         continue
                     else:
                         key, value = line.split('=', 1)
+                    if self.squash_config_y and value == 'y':
+                        value = '1'
                     config[key] = value
         return config
 
@@ -659,7 +669,7 @@
 
             if read_config:
                 output_dir = self.GetBuildDir(commit_upto, target)
-                for name in CONFIG_FILENAMES:
+                for name in self.config_filenames:
                     fname = os.path.join(output_dir, name)
                     config[name] = self._ProcessConfig(fname)
 
@@ -736,8 +746,8 @@
                                     line, board)
                         last_was_warning = is_warning
                         last_func = None
-            tconfig = Config(board.target)
-            for fname in CONFIG_FILENAMES:
+            tconfig = Config(self.config_filenames, board.target)
+            for fname in self.config_filenames:
                 if outcome.config:
                     for key, value in outcome.config[fname].iteritems():
                         tconfig.Add(fname, key, value)
@@ -1193,7 +1203,7 @@
                 arch_config_plus[arch] = {}
                 arch_config_minus[arch] = {}
                 arch_config_change[arch] = {}
-                for name in CONFIG_FILENAMES:
+                for name in self.config_filenames:
                     arch_config_plus[arch][name] = {}
                     arch_config_minus[arch][name] = {}
                     arch_config_change[arch][name] = {}
@@ -1210,7 +1220,7 @@
                 tbase = self._base_config[target]
                 tconfig = config[target]
                 lines = []
-                for name in CONFIG_FILENAMES:
+                for name in self.config_filenames:
                     if not tconfig.config[name]:
                         continue
                     config_plus = {}
@@ -1254,7 +1264,7 @@
                 all_plus = {}
                 all_minus = {}
                 all_change = {}
-                for name in CONFIG_FILENAMES:
+                for name in self.config_filenames:
                     all_plus.update(arch_config_plus[arch][name])
                     all_minus.update(arch_config_minus[arch][name])
                     all_change.update(arch_config_change[arch][name])