Core: Bring over some file related Switch changes.

Reducing the distance from the Switch port code.

Core/FileLoaders/DiskCachingFileLoader.cpp

@@ -21,6 +21,7 @@
 #include <mutex>
 #include <cstring>
 
+#include "ppsspp_config.h"
 #include "file/file_util.h"
 #include "file/free.h"
 #include "util/text/utf8.h"
@@ -29,6 +30,11 @@
 #include "Core/FileLoaders/DiskCachingFileLoader.h"
 #include "Core/System.h"
 
+#if PPSSPP_PLATFORM(SWITCH)
+// Far from optimal, but I guess it works...
+#define fseeko fseek
+#endif
+
 static const char *CACHEFILE_MAGIC = "ppssppDC";
 static const s64 SAFETY_FREE_DISK_SPACE = 768 * 1024 * 1024; // 768 MB
 // Aim to allow this many files cached at once.