scons: Hook in the listnewconfig kconfig helper.

This helper lists config options which are new in the Kconfig and which
are not currently set in the config file.

Change-Id: I0c426d85c0cf0d2bdbac599845669165285a82a0

SConstruct

@@ -261,6 +261,7 @@ Targets:
 
 kconfig_actions = (
     'defconfig',
+    'listnewconfig',
     'menuconfig',
     'setconfig',
 )
@@ -293,6 +294,13 @@ Kconfig tools:
         scons defconfig build/foo/bar build_opts/MIPS
 
 
+        listnewconfig:
+        Lists config options which are new in the Kconfig and which are not
+        currently set in the existing config file.
+
+        scons listnewconfig build/foo/bar
+
+
         menuconfig:
         Opens the menuconfig editor which will let you view and edit config
         values, and view help text. menuconfig runs in text mode.
@@ -831,6 +839,9 @@ for variant_path in variant_paths:
             defconfig_path = makePathAbsolute(kconfig_args[0])
             kconfig.defconfig(env, kconfig_file.abspath,
                     defconfig_path, config_file.abspath)
+        elif kconfig_action == 'listnewconfig':
+            kconfig.listnewconfig(env, kconfig_file.abspath,
+                    config_file.abspath)
         elif kconfig_action == 'menuconfig':
             kconfig.menuconfig(env, kconfig_file.abspath, config_file.abspath,
                     variant_path)

site_scons/gem5_scons/kconfig.py

@@ -30,6 +30,7 @@ import kconfiglib
 
 _kconfig_helpers = {
     "DEFCONFIG_PY": "defconfig.py",
+    "LISTNEWCONFIG_PY": "listnewconfig.py",
     "MENUCONFIG_PY": "menuconfig.py",
     "SETCONFIG_PY": "setconfig.py",
 }
@@ -93,6 +94,18 @@ def defconfig(env, base_kconfig, config_in, config_out):
         error("Failed to run defconfig")
 
 
+def listnewconfig(env, base_kconfig, config_path):
+    """
+    Interface of handling listnewconfig.py of Kconfiglib
+    """
+    kconfig_env = _prep_env(env, base_kconfig, config_path)
+    # Provide a little visual separation between SCons output and
+    # listnewconfig output.
+    print()
+    if kconfig_env.Execute('"${LISTNEWCONFIG_PY}" "${BASE_KCONFIG}"') != 0:
+        error("Failed to run listnewconfig")
+
+
 def menuconfig(
     env, base_kconfig, config_path, main_menu_text, style="aquatic"
 ):