https://gitlab.com/ixion/ixion/-/commit/1992b8ab9c7765b8da06b6054bb3c0ab990c62f7
https://bugs.gentoo.org/793917

From: Jory Pratt <anarchy@gentoo.org>
Date: Wed, 2 Jun 2021 10:19:01 -0500
Subject: [PATCH] Fix nullptr_t for clang/musl users

--- a/src/libixion/model_context.cpp
+++ b/src/libixion/model_context.cpp
@@ -17,7 +17,7 @@
 
 namespace ixion {
 
-model_context::input_cell::input_cell(nullptr_t) : type(celltype_t::empty) {}
+model_context::input_cell::input_cell(std::nullptr_t) : type(celltype_t::empty) {}
 model_context::input_cell::input_cell(bool b) : type(celltype_t::boolean)
 {
     value.boolean = b;