https://bugs.gentoo.org/761541
--- a/src/libslic3r/miniz_extension.hpp	2021-01-11 08:01:51.000000000 -0500
+++ b/src/libslic3r/miniz_extension.hpp	2021-01-12 01:16:10.503404521 -0500
@@ -4,4 +4,5 @@
 #include <string>
 #include <miniz.h>
+#include <miniz_zip.h>
 
 namespace Slic3r {