kconfig: Refactor kconfig.py to use __main__ and argparse

Kconfig.py is not following the de-facto (real?) coding standards of
Zephyr. This commit refactors kconfig.py with two changes:

Use __main__ and def main().

Use argparse instead of sys.argv.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>

scripts/kconfig/kconfig.py

@@ -2,14 +2,13 @@
 # Modified from: https://github.com/ulfalizer/Kconfiglib/blob/master/examples/merge_config.py
 from kconfiglib import Kconfig, Symbol, BOOL, STRING, TRISTATE, TRI_TO_STR
 import sys
+import argparse
 
-if len(sys.argv) < 5:
-    print('usage: {} Kconfig dotconfig autoconf conf1 [conf2 ...]'
-          .format(sys.argv[0]))
-    sys.exit(1)
+def main():
+    parse_args()
 
-print("Parsing Kconfig tree in {}".format(sys.argv[1]))
-kconf = Kconfig(sys.argv[1])
+    print("Parsing Kconfig tree in {}".format(args.kconfig_root))
+    kconf = Kconfig(args.kconfig_root)
 
     # Enable warnings for assignments to undefined symbols
     kconf.enable_undef_warnings()
@@ -18,11 +17,11 @@ kconf.enable_undef_warnings()
     # up here as well. The approach in examples/allnoconfig_simpler.py could
     # provide an allnoconfig starting state for example.
 
-print("Using {} as base".format(sys.argv[4]))
-for config in sys.argv[5:]:
+    print("Using {} as base".format(args.conf_fragments[0]))
+    for config in args.conf_fragments[1:]:
         print("Merging {}".format(config))
     # Create a merged configuration by loading the fragments with replace=False
-for config in sys.argv[4:]:
+    for config in args.conf_fragments:
         kconf.load_config(config, replace=False)
 
 
@@ -66,7 +65,27 @@ for warning in kconf.warnings:
 
 
     # Write the merged configuration
-kconf.write_config(sys.argv[2])
+    kconf.write_config(args.dotconfig)
 
     # Write the C header
-kconf.write_autoconf(sys.argv[3])
+    kconf.write_autoconf(args.autoconf)
+
+
+def parse_args():
+    global args
+
+    parser = argparse.ArgumentParser(
+        description=__doc__,
+        formatter_class=argparse.RawDescriptionHelpFormatter
+    )
+
+    parser.add_argument("kconfig_root")
+    parser.add_argument("dotconfig")
+    parser.add_argument("autoconf")
+    parser.add_argument("conf_fragments", metavar='conf', type=str, nargs='+')
+
+    args = parser.parse_args()
+
+
+if __name__ == "__main__":
+    main()