message: fix: compile error with gcc 9.3 which is default in ubuntu 20.04
diff: @@ -2,6 +2,7 @@ CLEAN_FILES = # deliberately empty, so we can append below.
  CXX=g++
  PLATFORM_LDFLAGS= -lpthread -lrt
  PLATFORM_CXXFLAGS= -std=c++11 -fno-builtin-memcmp -msse -msse4.2
  +ROCKSDB_CXXFLAGS= -Wno-error=deprecated-copy -Wno-error=pessimizing-move -Wno-error=class-memaccess -Wno-error=array-bounds
  PROFILING_FLAGS=-pg
  OPT=
  LDFLAGS += -Wl,-rpath=$(RPATH)
  @@ -226,7 +227,7 @@ $(PINK):
  $(AM_V_at)make -C $(PINK_PATH)/pink/ DEBUG_LEVEL=$(DEBUG_LEVEL) NO_PB=0 SLASH_PATH=$(SLASH_PATH)
  $(ROCKSDB):
  - $(AM_V_at)make -j $(PROCESSOR_NUMS) -C $(ROCKSDB_PATH)/ static_lib DISABLE_JEMALLOC=1 DEBUG_LEVEL=$(DEBUG_LEVEL)
  + $(AM_V_at) CXXFLAGS='$(ROCKSDB_CXXFLAGS)' make -j $(PROCESSOR_NUMS) -C $(ROCKSDB_PATH)/ static_lib DISABLE_JEMALLOC=1 DEBUG_LEVEL=$(DEBUG_LEVEL)
  $(BLACKWIDOW):
  $(AM_V_at)make -C $(BLACKWIDOW_PATH) ROCKSDB_PATH=$(ROCKSDB_PATH) SLASH_PATH=$(SLASH_PATH) DEBUG_LEVEL=$(DEBUG_LEVEL)
  