filesystem: use std for IsFolder

Remove custom platform implementation of IsFolder and replace
single use with `std::filesystem::is_directory`.

src/xenia/base/filesystem.h

@@ -52,9 +52,6 @@ bool CreateFolder(const std::filesystem::path& path);
 // Returns true if the path was found and removed.
 bool DeleteFolder(const std::filesystem::path& path);
 
-// Returns true if the given path exists and is a folder.
-bool IsFolder(const std::filesystem::path& path);
-
 // Creates an empty file at the given path.
 bool CreateFile(const std::filesystem::path& path);
 

src/xenia/base/filesystem_posix.cc

@@ -137,14 +137,6 @@ static uint64_t convertUnixtimeToWinFiletime(time_t unixtime) {
   return filetime;
 }
 
-bool IsFolder(const std::filesystem::path& path) {
-  struct stat st;
-  if (stat(path.c_str(), &st) == 0) {
-    if (S_ISDIR(st.st_mode)) return true;
-  }
-  return false;
-}
-
 bool CreateFile(const std::filesystem::path& path) {
   int file = creat(path.c_str(), 0774);
   if (file >= 0) {

src/xenia/base/filesystem_win.cc

@@ -84,12 +84,6 @@ bool DeleteFolder(const std::filesystem::path& path) {
   return SHFileOperation(&op) == 0;
 }
 
-bool IsFolder(const std::filesystem::path& path) {
-  DWORD attrib = GetFileAttributes(path.c_str());
-  return attrib != INVALID_FILE_ATTRIBUTES &&
-         (attrib & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY;
-}
-
 bool CreateFile(const std::filesystem::path& path) {
   auto handle = CreateFileW(path.c_str(), 0, 0, nullptr, CREATE_ALWAYS,
                             FILE_ATTRIBUTE_NORMAL, nullptr);

src/xenia/vfs/devices/stfs_container_device.cc

@@ -61,7 +61,7 @@ StfsContainerDevice::~StfsContainerDevice() = default;
 
 bool StfsContainerDevice::Initialize() {
   // Resolve a valid STFS file if a directory is given.
-  if (filesystem::IsFolder(host_path_) && !ResolveFromFolder(host_path_)) {
+  if (std::filesystem::is_directory(host_path_) && !ResolveFromFolder(host_path_)) {
     XELOGE("Could not resolve an STFS container given path {}",
            xe::path_to_utf8(host_path_));
     return false;