frontend_common: Manually handle opening config file

SimpleIni only has the ability to use ANSI strings for config paths so this breaks opening configs on paths with special characters. This ensures that we open the right path on each platform.

src/frontend_common/config.cpp

@@ -16,6 +16,8 @@
 
 #include <boost/algorithm/string/replace.hpp>
 
+#include "common/string_util.h"
+
 namespace FS = Common::FS;
 
 Config::Config(const ConfigType config_type)
@@ -56,16 +58,43 @@ void Config::Initialize(const std::optional<std::string> config_path) {
 }
 
 void Config::WriteToIni() const {
-    if (const SI_Error rc = config->SaveFile(config_loc.c_str(), false); rc < 0) {
+    FILE* fp = nullptr;
+#ifdef _WIN32
+    fp = _wfopen(Common::UTF8ToUTF16W(config_loc).data(), L"wb");
+#else
+    fp = fopen(config_loc.c_str(), "wb");
+#endif
+
+    CSimpleIniA::FileWriter writer(fp);
+    const SI_Error rc = config->Save(writer, false);
+    if (rc < 0) {
         LOG_ERROR(Frontend, "Config file could not be saved!");
     }
+    fclose(fp);
 }
 
 void Config::SetUpIni() {
     config = std::make_unique<CSimpleIniA>();
     config->SetUnicode(true);
     config->SetSpaces(false);
-    config->LoadFile(config_loc.c_str());
+
+    FILE* fp = nullptr;
+#ifdef _WIN32
+    _wfopen_s(&fp, Common::UTF8ToUTF16W(config_loc).data(), L"rb, ccs=UTF-8");
+    if (fp == nullptr) {
+        fp = _wfopen(Common::UTF8ToUTF16W(config_loc).data(), L"wb, ccs=UTF-8");
+    }
+#else
+    fp = fopen(config_loc.c_str(), "rb");
+    if (fp == nullptr) {
+        fp = fopen(config_loc.c_str(), "wb");
+    }
+#endif
+
+    if (SI_Error rc = config->LoadFile(fp); rc < 0) {
+        LOG_ERROR(Frontend, "Config file could not be loaded!");
+    }
+    fclose(fp);
 }
 
 bool Config::IsCustomConfig() const {