$NetBSD$

Use GTK3, since that's how we build wxWidgets.

--- CMakeLists.txt.orig	2021-01-11 13:01:51.000000000 +0000
+++ CMakeLists.txt
@@ -33,7 +33,7 @@ option(SLIC3R_MSVC_PDB          "Generat
 option(SLIC3R_PERL_XS           "Compile XS Perl module and enable Perl unit and integration tests" 0)
 option(SLIC3R_ASAN              "Enable ASan on Clang and GCC" 0)
 
-set(SLIC3R_GTK "2" CACHE STRING "GTK version to use with wxWidgets on Linux")
+set(SLIC3R_GTK "3" CACHE STRING "GTK version to use with wxWidgets on Linux")
 
 if (APPLE)
     set(CMAKE_FIND_FRAMEWORK LAST)
