extractor: cleanup, support unicode properly, and add multi-game support (#1609)

* extractor: refactor and cleanup for multi-game support

* deps: switch to `ghc::filesystem` as it is utf-8 everywhere by default

* extractor: finally working with unicode

* unicode: fix unicode cli args on windows in all `main` functions

common/util/unicode_util.cpp

@@ -0,0 +1,61 @@
+#include "unicode_util.h"
+
+// clang-format off
+#ifdef _WIN32
+#define NOMINMAX
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <stdio.h>
+#include <Stringapiset.h>
+#include <processenv.h>
+#include <winbase.h>
+#include <shellapi.h>
+#undef FALSE
+#endif
+// clang-format on
+
+std::string utf8_from_utf16(const wchar_t* utf16_string) {
+#ifdef _WIN32
+  if (utf16_string == nullptr) {
+    return std::string();
+  }
+  int target_length = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string, -1, nullptr,
+                                          0, nullptr, nullptr);
+  if (target_length == 0) {
+    return std::string();
+  }
+  std::string utf8_string;
+  utf8_string.resize(target_length);
+  int converted_length = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string, -1,
+                                             utf8_string.data(), target_length, nullptr, nullptr);
+  if (converted_length == 0) {
+    return std::string();
+  }
+  return utf8_string;
+#else
+  return "don't call this on linux";
+#endif
+}
+
+std::vector<std::string> get_widechar_cli_args() {
+#ifdef _WIN32
+  // Convert the UTF-16 command line arguments to UTF-8 for the Engine to use.
+  int argc;
+  wchar_t** argv = CommandLineToArgvW(GetCommandLineW(), &argc);
+  if (argv == nullptr) {
+    return {};
+  }
+
+  std::vector<std::string> command_line_arguments;
+
+  for (int i = 0; i < argc; i++) {
+    command_line_arguments.push_back(utf8_from_utf16(argv[i]));
+  }
+
+  LocalFree(argv);
+
+  return command_line_arguments;
+#else
+  return {"don't call this on linux"};
+#endif
+}