Only show the "--software-renderer" option if GUI is compiled in.

src/libslic3r/PrintConfig.cpp

@@ -3118,7 +3118,7 @@ CLIMiscConfigDef::CLIMiscConfigDef()
     def->tooltip = L("Messages with severity lower or eqal to the loglevel will be printed out. 0:trace, 1:debug, 2:info, 3:warning, 4:error, 5:fatal");
     def->min = 0;
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && defined(SLIC3R_GUI)
     def = this->add("sw_renderer", coBool);
     def->label = L("Render with a software renderer");
     def->tooltip = L("Render with a software renderer. The bundled MESA software renderer is loaded instead of the default OpenGL driver.");