Building driver results in BTF warning

building driver module for older kernels was no issue. But now with a RHEL9 kernel (5.14.0-70.13.1.el9_0.x86_64) the following warning is output.
"Skipping BTF generation for 'my_driver.ko' due to unavailability of vmlinux"
Presumably either something has moved, or something is missing from our installation.