undefined reference to `i2cWriteByteData'

Same problem as:
https://github.com/folkhack/adxl345spi/commit/93c8b0a752d38f35b6d199f3c328b1c04f1d880b

new make file:

```
LDFLAGS=-lpigpio
CFLAGS=-Wall
CC=gcc
LIBS = -L /usr/local/include -lpigpio -lrt

all:
        $(CC) $(CFLAGS) test.c $(LIBS) -o test

clean:
        rm -f test

```