Fix coompilation on windows

Some Windows enviroments don't have uint64_t, and we dont really need
that type. Assume 64-bit integers take 8 bytes.

storage/rocksdb/build_rocksdb.cmake

@@ -31,9 +31,8 @@ endif()
 
 include (CheckTypeSize)
 check_type_size(size_t SIZEOF_SIZE_T)
-check_type_size(uint64_t SIZEOF_UINT64_T)
 set_property(SOURCE ha_rocksdb.cc APPEND PROPERTY COMPILE_DEFINITIONS
-  SIZEOF_SIZE_T=${SIZEOF_SIZE_T} SIZEOF_UINT64_T=${SIZEOF_UINT64_T})
+  SIZEOF_SIZE_T=${SIZEOF_SIZE_T} SIZEOF_UINT64_T=8)
 
 # Optional compression libraries.