Add demos to CMake

demos/src/demo_sm9_keygen.c

@@ -0,0 +1,35 @@
+/*
+ *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the License); you may
+ *  not use this file except in compliance with the License.
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <gmssl/sm9.h>
+
+
+int main(void)
+{
+	SM9_SIGN_MASTER_KEY sign_master;
+	SM9_SIGN_KEY sign_key;
+
+	sm9_sign_master_key_generate(&sign_master);
+
+	printf("SM9 Master Secret\n");
+	sm9_sign_master_key_info_encrypt_to_pem(&sign_master, "P@ssw0rd", stdout);
+
+	printf("SM9 Public Parameters\n");
+	sm9_sign_master_public_key_to_pem(&sign_master, stdout);
+
+	sm9_sign_master_key_extract_key(&sign_master, "alice", strlen("alice"), &sign_key);
+
+	printf("SM9 private key for ID '%s'\n", "alice");
+	sm9_sign_key_info_encrypt_to_pem(&sign_key, "123456", stdout);
+
+	return 0;
+}