Patch RbNaCl to find system libsodium

The patch is taken from this PR
RubyCrypto/rbnacl#186.

packages/plugins/rubygem-rbnacl/0001-Added-support-for-Heroku.patch

@@ -0,0 +1,36 @@
+From 38c1bcd2fe7a3735c52fdd9dd9127814cbcc44e6 Mon Sep 17 00:00:00 2001
+From: Andrew Kane <[email protected]>
+Date: Sat, 1 Dec 2018 15:03:36 -0800
+Subject: [PATCH] Added support for Heroku
+
+---
+ lib/rbnacl/init.rb   | 2 +-
+ lib/rbnacl/sodium.rb | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/lib/rbnacl/init.rb b/lib/rbnacl/init.rb
+index cd0168b..a3cc12b 100644
+--- a/lib/rbnacl/init.rb
++++ b/lib/rbnacl/init.rb
+@@ -5,7 +5,7 @@ module RbNaCl
+   # Defines the libsodium init function
+   module Init
+     extend FFI::Library
+-    ffi_lib "sodium"
++    ffi_lib ["sodium", "libsodium.so.18", "libsodium.so.23"]
+
+     attach_function :sodium_init, [], :int
+   end
+diff --git a/lib/rbnacl/sodium.rb b/lib/rbnacl/sodium.rb
+index c72b000..f12ac45 100644
+--- a/lib/rbnacl/sodium.rb
++++ b/lib/rbnacl/sodium.rb
+@@ -8,7 +8,7 @@ module RbNaCl
+   module Sodium
+     def self.extended(klass)
+       klass.extend FFI::Library
+-      klass.ffi_lib "sodium"
++      klass.ffi_lib ["sodium", "libsodium.so.18", "libsodium.so.23"]
+     end
+
+     def sodium_type(type = nil)

packages/plugins/rubygem-rbnacl/rubygem-rbnacl.spec

@@ -13,6 +13,7 @@ Group: Development/Languages
 License: MIT
 URL: https://github.com/cryptosphere/rbnacl
 Source0: https://rubygems.org/gems/%{gem_name}-%{version}.gem
+Patch0: 0001-Added-support-for-Heroku.patch
 
 # start specfile generated dependencies
 Requires: %{?scl_prefix_ruby}ruby(release)