flt.lttng-utils.debug-info: Replace hardcoded '/' in paths

flt.lttng-utils.debug-info: Replace hardcoded '/' in paths

Replace hardcoded '/' directory separators with glib functions that will
automatically select the proper separator per platform.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Change-Id: I53195657f6514930998979612c6b04de5e3c1dd8
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1336
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>