fs/FileSystem: add CreateDirectoryNoThrow()

src/fs/FileSystem.hxx

@@ -67,6 +67,16 @@ StatFile(Path file, struct stat &buf, bool follow_symlinks = true)
 
 #endif
 
+static inline bool
+CreateDirectoryNoThrow(Path path) noexcept
+{
+#ifdef _WIN32
+	return CreateDirectory(path.c_str(), nullptr);
+#else
+	return mkdir(path.c_str(), 0777);
+#endif
+}
+
 /**
  * Truncate a file that exists already.  Throws std::system_error on
  * error.

src/fs/StandardDirectory.cxx

@@ -314,7 +314,7 @@ GetAppRuntimeDir() noexcept
 #ifdef USE_XDG
 	if (const auto user_dir = GetUserRuntimeDir(); !user_dir.IsNull()) {
 		auto dir = user_dir / app_filename;
-		mkdir(dir.c_str(), 0777);
+		CreateDirectoryNoThrow(dir);
 		return dir;
 	}
 #endif