Build external override library with all symbols

The curve25519 depends on ssh_get_random, which is normally built into libssh.
For the external override tests to build, we need to have them in separate
source file that can be included for this test.

For some reason, this did not happen on CI builds, but it did happen in koji
during RPM builds.

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/getrandom_gcrypt.c

@@ -0,0 +1,38 @@
+/*
+ * This file is part of the SSH Library
+ *
+ * Copyright (c) 2009 by Aris Adamantiadis
+ * Copyright (C) 2016 g10 Code GmbH
+ *
+ * The SSH Library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * The SSH Library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the SSH Library; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "libssh/crypto.h"
+#include <gcrypt.h>
+
+int
+ssh_get_random(void *where, int len, int strong)
+{
+    /* variable not used in gcrypt */
+    (void)strong;
+
+    /* not using GCRY_VERY_STRONG_RANDOM which is a bit overkill */
+    gcry_randomize(where, len, GCRY_STRONG_RANDOM);
+
+    return 1;
+}