SDK archive missing staging_dir/target** directory

In the past I had been building the firmware for a RUT955 router and in this build the cross-compiled libraries were always located in the sdk artifact in the directory staging_dir/target-mips_34kc_uClibc-

Now I'm switching to a RUTX09 device and building the Firmware for this too. Unfortunately the sdk artifact built in bin/targets/ipq40xx/generic/openwrt-sdk-ipq40xx-generic_gcc-7.5.0_musl_eabi.Linux-x86_64.tar.xz doesn't seem to pack up the target directory. I can see the directory exists in the original directory structure and it contains the things I'm looking for, but that's not included in the archive.

I know I could simply zip up that directory, but I think perhaps I configured something wrongly. And therefor am asking you folks: Is there any setting or option I possibly didn't select?