1.18.0 does not compile w/o `/sys/kernel/btf/vmlinux` required for queue_track backend

Build environment sometimes does not have full sysfs mounted (for example to slightly increase build security or for reproducible builds) or [build-time] kernel does not have DEBUG_INFO_BTF enabled (sometimes just for some architecture where huge kernel does not fit into u-boot). In that case stalld does not compile because it requires access to /sys/kernel/btf/vmlinux. (And of course there is rarely access to /boot/vmlinux-* because it resides in (huge) -debuginfo package and normal kernel is vmlinuz.)

It would be useful to be able to select at build time to compile stalld without eBPF/queue_track support.