MDEV-13852 - redefine WinWriteableFile such as IsSyncThreadSafe()

is set to true, as it should.

Copy and modify original io_win.h header file to a different location
(as we cannot patch anything in submodule). Make sure modified header is
used.

storage/rocksdb/build_rocksdb.cmake

@@ -11,6 +11,11 @@ INCLUDE_DIRECTORIES(
   ${ROCKSDB_SOURCE_DIR}/third-party/gtest-1.7.0/fused-src
 )
 
+IF(WIN32)
+  INCLUDE_DIRECTORIES(BEFORE
+  ${CMAKE_CURRENT_SOURCE_DIR}/patch)
+ENDIF()
+
 list(APPEND CMAKE_MODULE_PATH "${ROCKSDB_SOURCE_DIR}/cmake/modules/")
 
 if(WIN32)

storage/rocksdb/mysql-test/rocksdb/suite.pm

@@ -23,7 +23,6 @@ $ENV{MARIAROCKS_SST_DUMP}="$sst_dump";
 # Temporarily disable testing under valgrind, due to MDEV-12439 
 return "RocksDB tests disabled under valgrind" if ($::opt_valgrind);
 
-return "Temporarily disabled on Windows due to MDEV-13852" if (My::SysInfo::IS_WINDOWS);
 
 bless { };