https://github.com/prusa3d/PrusaSlicer/commit/62592ca
https://bugs.gentoo.org/788196

From 62592cab48cfb6a20d84041b1992aecc6a2b659c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luk=C3=A1=C5=A1=20Hejl?= <hejl.lukas@gmail.com>
Date: Sat, 1 May 2021 22:33:59 +0200
Subject: [PATCH] Added missing include (GCC 11.1)

---
 src/libslic3r/Optimize/Optimizer.hpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libslic3r/Optimize/Optimizer.hpp b/src/libslic3r/Optimize/Optimizer.hpp
index 05191eba26..8ae55c61c5 100644
--- a/src/libslic3r/Optimize/Optimizer.hpp
+++ b/src/libslic3r/Optimize/Optimizer.hpp
@@ -8,6 +8,7 @@
 #include <functional>
 #include <limits>
 #include <cassert>
+#include <optional>
 
 namespace Slic3r { namespace opt {
 
