Externals/FatFs: Build as part of Dolphin.

Co-authored-by: Pablo Stebler <pablo@stebler.xyz>

Source/Core/Common/FatFsUtil.cpp

@@ -0,0 +1,78 @@
+// Copyright 2022 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <cstdlib>
+#include <mutex>
+
+// Does not compile if diskio.h is included first.
+// clang-format off
+#include "ff.h"
+#include "diskio.h"
+// clang-format on
+
+// For now this is just mostly dummy functions so FatFs actually links.
+
+extern "C" DSTATUS disk_status(BYTE pdrv)
+{
+  return STA_NOINIT;
+}
+
+extern "C" DSTATUS disk_initialize(BYTE pdrv)
+{
+  return STA_NOINIT;
+}
+
+extern "C" DRESULT disk_read(BYTE pdrv, BYTE* buff, LBA_t sector, UINT count)
+{
+  return RES_PARERR;
+}
+
+extern "C" DRESULT disk_write(BYTE pdrv, const BYTE* buff, LBA_t sector, UINT count)
+{
+  return RES_PARERR;
+}
+
+extern "C" DRESULT disk_ioctl(BYTE pdrv, BYTE cmd, void* buff)
+{
+  return RES_PARERR;
+}
+
+extern "C" DWORD get_fattime(void)
+{
+  return 0;
+}
+
+extern "C" void* ff_memalloc(UINT msize)
+{
+  return std::malloc(msize);
+}
+
+extern "C" void ff_memfree(void* mblock)
+{
+  return std::free(mblock);
+}
+
+extern "C" int ff_cre_syncobj(BYTE vol, FF_SYNC_t* sobj)
+{
+  *sobj = new std::recursive_mutex();
+  return *sobj != nullptr;
+}
+
+extern "C" int ff_req_grant(FF_SYNC_t sobj)
+{
+  std::recursive_mutex* m = reinterpret_cast<std::recursive_mutex*>(sobj);
+  m->lock();
+  return 1;
+}
+
+extern "C" void ff_rel_grant(FF_SYNC_t sobj)
+{
+  std::recursive_mutex* m = reinterpret_cast<std::recursive_mutex*>(sobj);
+  m->unlock();
+}
+
+extern "C" int ff_del_syncobj(FF_SYNC_t sobj)
+{
+  delete reinterpret_cast<std::recursive_mutex*>(sobj);
+  return 1;
+}