Build failure bft for trace-cmd and libtraceevent

Hi Steven, All,

in Buildroot I'm bumping libtraceevent to 1.9.0 and trace-cmd to 3.4 and
experiencing build failures because of the change of uapi/linux/bft.h
defines/enums

I see as possible solution to create a bft_compat.h to deal with
different Linux versions, but this is not a quick solution.

Otherwise the solution could be to switch according to Linux version
between print_args() with and without bft support, basically re-adding
the function here:
https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/commit/?id=e798103c0815e6642e74d9317c325b2c62681f2e

What do you think about it?

Best regards
Giulio Benetti