systemd.pc: Keep support for rootprefix and root_prefix... ...support for split-usr in https://github.com/systemd/systemd/commit/b0d3095fd6cc... With https://github.com/systemd/systemd/commit/b0d3095fd6cc... - [0](https://github.com/fwupd/fwupd/blob/caa788b37ff34334d8... - [2](https://github.com/PipeWire/pipewire/blob/49cdb468c28b...