[werk_ag]

... For some reason, I had it in my head that the WD software downloads had all the extra drivers already included in them.

And you are right! Each software package includes all the required libraries to compile.

The SHT1X library is included on the WeatherDuino_Pro2_Universal_TX_v7.0_b003, exactly the version you are trying to compile, please double check the libraries folder on the WeatherDuino_Pro2_Universal_TX_v7.0_b003.zip file.

Rgs.
Werk_AG