Fix: flt.lttng-utils.debug-info: build id note section non-native byte order

Issue
=====
The build id comparison code does not take into account that the target
binary file could be compiled for another architecture and thus could be
of a different byte order. This makes the build_id testcase fail on
PowerPC. The artefacts used for this testcase are compiled on x86 and
are thus in little endian as opposed to PowerPC's big endianness.

Solution
========
Parse the Elf file to extract the endianness of the binary and use that
information to change the byte order of the note section if necessary.

Drawbacks
=========
None.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Id5d761832f9463b38ea0452da36053e885929aa9
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1246
Reviewed-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>