kconfig: improve error messages for bad source statements

We now say where we detect the second source of a file,
and where we detect a recursively source of the same file.
This makes it easier to fix such errors.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Roman Zippel <zippel@linux-m68k.org>

scripts/kconfig/zconf.l

@@ -314,11 +314,14 @@ void zconf_nextfile(const char *name)
 	current_buf = buf;
 
 	if (file->flags & FILE_BUSY) {
-		printf("recursive scan (%s)?\n", name);
+		printf("%s:%d: do not source '%s' from itself\n",
+		       zconf_curname(), zconf_lineno(), name);
 		exit(1);
 	}
 	if (file->flags & FILE_SCANNED) {
-		printf("file %s already scanned?\n", name);
+		printf("%s:%d: file '%s' is already sourced from '%s'\n",
+		       zconf_curname(), zconf_lineno(), name,
+		       file->parent->name);
 		exit(1);
 	}
 	file->flags |= FILE_BUSY;