Disable -Werror for rocksdb submodule

We cannot have -Werror for third-party submodules because
whenever they break the build we cannot fix it as needed.

storage/rocksdb/CMakeLists.txt

@@ -253,7 +253,7 @@ CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/myrocks_hotbackup.py
 INSTALL_SCRIPT(${CMAKE_CURRENT_BINARY_DIR}/myrocks_hotbackup COMPONENT rocksdb-engine)
 
 IF(CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-  SET_TARGET_PROPERTIES(rocksdb_tools sst_dump mysql_ldb PROPERTIES COMPILE_FLAGS -frtti)
+  SET_TARGET_PROPERTIES(rocksdb_tools sst_dump mysql_ldb PROPERTIES COMPILE_FLAGS "-frtti -Wno-error")
 ENDIF()
 IF(MSVC)
   # RocksDB, the storage engine, overdoes "const" by adding

storage/rocksdb/build_rocksdb.cmake

@@ -471,6 +471,6 @@ list(APPEND SOURCES ${CMAKE_CURRENT_BINARY_DIR}/build_version.cc)
 ADD_CONVENIENCE_LIBRARY(rocksdblib ${SOURCES})
 target_link_libraries(rocksdblib ${THIRDPARTY_LIBS} ${SYSTEM_LIBS})
 IF(CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-  set_target_properties(rocksdblib PROPERTIES COMPILE_FLAGS "-fPIC -fno-builtin-memcmp -frtti")
+  set_target_properties(rocksdblib PROPERTIES COMPILE_FLAGS "-fPIC -fno-builtin-memcmp -frtti -Wno-error")
 endif()