pkg-config is the way devel libs are telling to the devel environment how to use them - which -I, -l & -L and other compiler and linker options to use, etc. Without that - options should be provided explicitly.
Looking at https://rpmfind.net/linux/RPM/opensu...1.armv7hl.html I'd say Jolla/Sailfish has a little to do with it, it's rather up-up-up-stream problem. Could be fixed by re-packaging with all the necessary data but it's not core package so why care (from the vendor perspective).