Copied from Harmony version 1.06, 
found at {HARMONY_INSTALL_DIR}/v1_06/framework/system

On my local machine, that's D:/PIC/Harmony/v1_06/framework/system,
subdirectories ./clk, ./devcon, and ./int

Note also that I had to manually add the plib library to the project.
Under Project Properties, go to Libraries, and add
{HARMONY_INSTALL_DIR}/v1_06/bin/framework/peripheral/PIC32MX470F512L_peripherals.a