kconfig: warn no new line at end of file

It would be nice to warn if a new line is missing at end of file.

We could do this by checkpatch.pl for arbitrary files, but new line
is rather essential as a statement terminator in Kconfig.

The warning message looks like this:

  kernel/Kconfig.preempt:60:warning: no new line at end of file

Currently, kernel/Kconfig.preempt is the only file with no new line
at end of file. Fix it.

I know there are some false negative cases. For example, no warning
is displayed when the last line contains some whitespaces/comments,
but no new line. Yet, this commit works well for most cases.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

kernel/Kconfig.preempt

@@ -57,4 +57,4 @@ config PREEMPT
 endchoice
 
 config PREEMPT_COUNT
-       bool
\ No newline at end of file
+       bool

scripts/kconfig/zconf.l

@@ -261,6 +261,10 @@ n	[A-Za-z0-9_-]
 <<EOF>>	{
 	BEGIN(INITIAL);
 
+	if (prev_token != T_EOL && prev_token != T_HELPTEXT)
+		fprintf(stderr, "%s:%d:warning: no new line at end of file\n",
+			current_file->name, yylineno);
+
 	if (current_file) {
 		zconf_endfile();
 		return T_EOL;