I also needed lpthread so that I could install the i2c-bus module for the bme280-sensor package. Ended up running the code below and it worked.
ar -rc /usr/lib/libpthread.a
This created the missing file. Now npm has installed both i2c-bus and bme280-sensor.
Thanks to @Trey-Felton from this post:
https://community.onion.io/topic/3546/serialport-with-node-v8-10-0/2