This is where you will find your natively packaged builds after the build has completed. On Windows these would live in:
workdir/*/installation/LibreOffice_Dev/native/install/en-US/*.msi
for example (nothing like a few long directory names before breakfast).
Also generates .ini files for the instdir/ tree (which are unfortunately duplicated for now between instsetoo_native/CustomTarget_setup.mk and scp2).