kconfig: fix failing to generate auto.conf

When the KCONFIG_AUTOCONFIG is specified (e.g. export \
KCONFIG_AUTOCONFIG=output/config/auto.conf), the directory of
include/config/ will not be created, so kconfig can't create deps
files in it and auto.conf can't be generated.
Signed-off-by: NJing Leng <jleng@ambarella.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/confdata.c

@@ -994,14 +994,19 @@ static int conf_write_autoconf_cmd(const char *autoconf_name)
 
 static int conf_touch_deps(void)
 {
-	const char *name;
+	const char *name, *tmp;
 	struct symbol *sym;
 	int res, i;
 
-	strcpy(depfile_path, "include/config/");
-	depfile_prefix_len = strlen(depfile_path);
-
 	name = conf_get_autoconfig_name();
+	tmp = strrchr(name, '/');
+	depfile_prefix_len = tmp ? tmp - name + 1 : 0;
+	if (depfile_prefix_len + 1 > sizeof(depfile_path))
+		return -1;
+
+	strncpy(depfile_path, name, depfile_prefix_len);
+	depfile_path[depfile_prefix_len] = 0;
+
 	conf_read_simple(name, S_DEF_AUTO);
 	sym_calc_value(modules_sym);