ENH: Format: Add ModelIO support on macOS

Github pull request: #2439

Change-Id: I4464a735a0a20b3e8103a344a64500b3d14b70e6

src/libslic3r/Format/ModelIO.hpp

@@ -0,0 +1,19 @@
+#include <string>
+
+namespace Slic3r {
+    /**
+     * Uses ModelIO to convert supported model types to a temporary STL
+     * that can then be consumed by the existing STL loader
+     * @param input_file The File to load
+     * @return Path to the temporary file, or an empty string if conversion failed
+     */
+    std::string make_temp_stl_with_modelio(const std::string &input_file);
+
+    /**
+     * Convenience function to delete the file.
+     * No return value since success isn't required
+     * @param temp_file File path to delete
+     */
+    void delete_temp_file(const std::string &temp_file);
+}
+