libyaml-cpp: fix compilation with libcxx

Added GitHub patch.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/libyaml-cpp/patches/010-libcxx.patch

@@ -0,0 +1,23 @@
+From 78f338e4ee69bb00fb37faf50f448eeedc8b824c Mon Sep 17 00:00:00 2001
+From: Mark Jan van Kampen <mjvk@allseas.com>
+Date: Tue, 13 Oct 2020 11:19:57 +0200
+Subject: [PATCH] Adds assert to enable compilation with libcxx+gcc
+
+Somehow this instantiates a template properly otherwise the build fails
+---
+ include/yaml-cpp/node/iterator.h | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/include/yaml-cpp/node/iterator.h b/include/yaml-cpp/node/iterator.h
+index b4472381..080ec76c 100644
+--- a/include/yaml-cpp/node/iterator.h
++++ b/include/yaml-cpp/node/iterator.h
+@@ -15,6 +15,8 @@
+ #include <utility>
+ #include <vector>
+ 
++static_assert(std::is_constructible<YAML::Node, const YAML::Node&>::value, "Node must be copy constructable");
++
+ namespace YAML {
+ namespace detail {
+ struct iterator_value : public Node, std::pair<Node, Node> {