csprng: fix cross-compiling against other libc implementations than glibc

Note:

This change assumes that the libc used implements a "gnu compatible" malloc.

security/csprng/csprng.conf

@@ -0,0 +1,19 @@
+# --- SDE-COPYRIGHT-NOTE-BEGIN ---
+# This copyright note is auto-generated by ./scripts/Create-CopyPatch.
+#
+# Filename: package/.../csprng/csprng.conf
+# Copyright (C) 2013 The OpenSDE Project
+#
+# More information can be found in the files COPYING and README.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License. A copy of the
+# GNU General Public License can be found in the file COPYING.
+# --- SDE-COPYRIGHT-NOTE-END ---
+
+# cross-compiling help
+if atstage cross; then
+	# always assuming a "gnu compatible" malloc
+	var_append configcache ' ' "ac_cv_func_malloc_0_nonnull=yes"
+fi