Compiling just with a little modification on makefile

[rodrigozago]

If someone else is facing issues to compile:

I tried to compile and i needed to add src/spi.c in the makefile on these lines:

on bin/tcl_server, bin/apa102_server, bin/ws2801_server and bin/lpd8806_server rules, like this.
gcc ${CFLAGS} -o $@ src/tcl_server.c src/opc_server.c src/spi.c src/cli.c