Fix of Boost 1.79 deprecated boost::filesystem::ofstream #8238

Replacing boost::filesystem::fstream with boost::nowide::fstream
variants with the unfortunate cost of string path conversion on Windows
from 16 bits to UTF8 and back to 16 bits.

Unfortunately we cannot use std::filesystem yet as it is missing
on older MACs and because the interface is crooked minefield on Windows
see https://github.com/microsoft/STL/issues/909

src/libslic3r/Preset.cpp

@@ -84,7 +84,7 @@ ConfigFileType guess_config_file_type(const ptree &tree)
 VendorProfile VendorProfile::from_ini(const boost::filesystem::path &path, bool load_all)
 {
     ptree tree;
-    boost::filesystem::ifstream ifs(path);
+    boost::nowide::ifstream ifs(path.string());
     boost::property_tree::read_ini(ifs, tree);
     return VendorProfile::from_ini(tree, path, load_all);
 }