message: Fix memory leak in get_environmental_variable()
diff: @@ -167,12 +167,13 @@ namespace vcpkg::System
  if (sz == 0)
  return nullopt;
  - auto ret = std::make_unique<std::wstring>(sz, L'\0');
  - Checks::check_exit(VCPKG_LINE_INFO, MAXDWORD >= ret->size());
  - auto sz2 = GetEnvironmentVariableW(varname, ret->data(), static_cast<DWORD>(ret->size()));
  + std::wstring ret(sz, L'\0');
  +
  + Checks::check_exit(VCPKG_LINE_INFO, MAXDWORD >= ret.size());
  + auto sz2 = GetEnvironmentVariableW(varname, ret.data(), static_cast<DWORD>(ret.size()));
  Checks::check_exit(VCPKG_LINE_INFO, sz2 + 1 == sz);
  - ret->pop_back();
  - return *ret.release();
  + ret.pop_back();
  + return ret;
  }
  static bool is_string_keytype(DWORD hkey_type)
  