AFAIK there is no wiringSerial library; everything is included in one of the standard libraries. I use the following in all my Makefiles
LDLIBS = -lwiringPi -lwiringPiDev -lpthread -lm
PS It is recommended you use /dev/serial0
serialPuts(fd,0xff); makes no sense "0xff" is NOT a "nul-terminated string" but it is unclear what you are trying to send (or why you don't just send a single string).