Fix GCC warnings to be ready for GCC standalone build

third_party/agg23/0001-gcc-warning.patch

Index: third_party/agg23/0001-gcc-warning.patch
diff --git a/third_party/agg23/0001-gcc-warning.patch b/third_party/agg23/0001-gcc-warning.patch
new file mode 100644
index 0000000000000000000000000000000000000000..759696ef03490badd5aab5393e63891a42644385
--- /dev/null
+++ b/third_party/agg23/0001-gcc-warning.patch
@@ -0,0 +1,17 @@
+diff --git a/third_party/agg23/agg_path_storage.h b/third_party/agg23/agg_path_storage.h
+index dc13851..7f21bac 100644
+--- a/third_party/agg23/agg_path_storage.h
++++ b/third_party/agg23/agg_path_storage.h
+@@ -38,9 +38,9 @@ public:
+         }
+         unsigned vertex(FX_FLOAT* x, FX_FLOAT* y)
+         {
+-            return (m_vertex_idx < m_path->total_vertices()) ?
+-                   m_path->vertex(m_vertex_idx++, x, y) :
+-                   path_cmd_stop;
++          return (m_vertex_idx < m_path->total_vertices())
++                     ? m_path->vertex(m_vertex_idx++, x, y)
++                     : static_cast<unsigned>(path_cmd_stop);
+         }
+     private:
+         const path_storage* m_path;