scripts: introduce .config/config.h generators

This patch introduces some scripts that takes a Kconfig script and generates
.config or config.h. These scripts are general and can be used by the
hypervisor, dm, tools, etc. as long as proper make targets are added.

Note: Kconfiglib by Ulf Magnusson is ISC licensed.

v4 -> v5:

    * Add minimalconfig which creates a defconfig by minimizing a given .config.

v3 -> v4:

    * silentoldconfig now properly generate a .config if an old one does not
      exist.

v2 -> v3:

    * Add license info and the permission notice of Kconfiglib.
    * Mention the input Kconfig in the script descriptions.

v1 -> v2:

    * Drop kconfiglib.py. The getting started guide will be updated accordingly
      and dependency checks will be added to Makefile in the following patches.

Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Zhao Yakui <yakui.zhao@intel.com>

scripts/kconfig/defconfig.py

@@ -0,0 +1,39 @@
+# Copyright (C) 2018 Intel Corporation.
+# SPDX-License-Identifier: BSD-3-Clause
+
+# This script takes a Kconfig and a defconfig file, and expands it to a .config
+# with all default values listed explicitly.
+
+import sys, os
+
+# Kconfiglib: Copyright (c) 2011-2018, Ulf Magnusson
+# SPDX-License-Identifier: ISC
+# Refer to scripts/kconfig/LICENSE.kconfiglib for the permission notice.
+import kconfiglib
+
+def usage():
+    sys.stdout.write("%s: <Kconfig file> <defconfig> <path to .config>\n" % sys.argv[0])
+
+def main():
+    if len(sys.argv) < 4:
+        usage()
+        sys.exit(1)
+
+    kconfig_path = sys.argv[1]
+    if not os.path.isfile(kconfig_path):
+        sys.stderr.write("Cannot find file %s\n" % kconfig_path)
+        sys.exit(1)
+
+    defconfig_path = sys.argv[2]
+    if not os.path.isfile(defconfig_path):
+        sys.stderr.write("Cannot find file %s\n" % defconfig_path)
+        sys.exit(1)
+
+    sys.stdout.write("Default configuration based on %s.\n" % defconfig_path)
+    kconfig = kconfiglib.Kconfig(kconfig_path)
+    kconfig.load_config(defconfig_path)
+    kconfig.write_config(sys.argv[3])
+    sys.stdout.write("Configuration written to %s.\n" % sys.argv[3])
+
+if __name__ == "__main__":
+    main()