arch/x86_64:Fix build cxx warning.

Signed-off-by: cuiziwei <[email protected]>

Author: cuiziweizw

arch/x86_64/src/common/Toolchain.defs

@@ -32,6 +32,9 @@ ifeq ($(CONFIG_FRAME_POINTER),y)
   ARCHOPTIMIZATION += -fno-omit-frame-pointer -fno-optimize-sibling-calls
 endif
 
+ARCHCFLAGS += -fno-common -Wno-attributes
+ARCHCXXFLAGS += -fno-common -Wno-attributes -nostdinc++
+
 ARCHCPUFLAGS = -fno-pic -mcmodel=large -fno-stack-protector -mno-red-zone -mrdrnd
 ARCHPICFLAGS = -fPIC
 ARCHWARNINGS = -Wall -Wstrict-prototypes -Wshadow -Wundef