firmware build error ASUS RT-N56U

make[3]: *** [scripts/Makefile.build:307: net/nat/hw_nat/ra_nat.o] Error 1 make[2]: *** [scripts/Makefile.build:443: net/nat/hw_nat] Error 2 make[1]: *** [Makefile:1000: net] Error 2 make: *** [Makefile:134: linux] Error 1