Fix build - 64 bit functions do not exist

include/vk_mem_alloc.h

diff --git a/include/vk_mem_alloc.h b/include/vk_mem_alloc.h
index 97e321c..7544c53 100644
--- a/include/vk_mem_alloc.h
+++ b/include/vk_mem_alloc.h
@@ -3074,7 +3074,7 @@
 

 static inline uint8_t VmaBitScanLSB(uint64_t mask)

 {

-#ifdef _MSC_VER

+#if defined(_MSC_VER) && defined(_WIN64)

     unsigned long pos;

     if (_BitScanForward64(&pos, mask))

         return static_cast<uint8_t>(pos);

@@ -3108,7 +3108,7 @@
 

 static inline uint8_t VmaBitScanMSB(uint64_t mask)

 {

-#ifdef _MSC_VER

+#if defined(_MSC_VER) && defined(_WIN64)

     unsigned long pos;

     if (_BitScanReverse64(&pos, mask))

         return static_cast<uint8_t>(pos);