lttng-tools-2.14.0-rc1: Not possible to disable babeltrace2 dependency

[Norbert Lange]

Hello,

I had to add babeltrace2_CFLAGS="-DA" babeltrace2_LIBS="-lm" to the
configure line
to be able to build.

There should be a --without-babeltrace2 switch and possible automatic detection.

Regards, Norbert