make fails part 2

[fnoop]

Related to #1

In file included from /usr/include/aarch64-linux-gnu/bits/byteswap.h:34:0,
                 from /usr/include/byteswap.h:24,
                 from /srv/maverick/var/build/jtx1inst/src/jtx1pow.c:17:
/srv/maverick/var/build/jtx1inst/src/jtx1pow.c: In function ‘convShuntVol’:
/srv/maverick/var/build/jtx1inst/src/jtx1pow.c:43:27: warning: implicit declaration of function ‘i2c_smbus_read_word_data’ [-Wimplicit-function-declaration]
   uint16_t v = __bswap_16(i2c_smbus_read_word_data(file, reg));
                           ^
/srv/maverick/var/build/jtx1inst/src/jtx1pow.c: In function ‘jtx1_get_ina3221_userspace_i2c’:
/srv/maverick/var/build/jtx1inst/src/jtx1pow.c:173:7: warning: implicit declaration of function ‘ioctl’ [-Wimplicit-function-declaration]
   if (ioctl(file, I2C_SLAVE, addr) < 0) {
       ^~~~~
/srv/maverick/var/build/jtx1inst/src/jtx1pow.c:203:10: warning: ‘return’ with a value, in function returning void
   return 0;

...

[100%] Linking C executable jtx1inst_demo
libjtx1inst.so: undefined reference to `i2c_smbus_read_word_data'
collect2: error: ld returned 1 exit status
CMakeFiles/jtx1inst_demo.dir/build.make:95: recipe for target 'jtx1inst_demo' failed
make[2]: *** [jtx1inst_demo] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/jtx1inst_demo.dir/all' failed
make[1]: *** [CMakeFiles/jtx1inst_demo.dir/all] Error 2
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2

If I install libi2c-dev and include i2c/smbus.h in src/jtx1pow.c it gets rid of the implicit declaration but still doesn't link.