meson: use message() rather than warning()

warning() was only added to the meson interpreter in 0.44 which is
currently the last version. Let's use message() as we are currently
requiring meson > 0.40. Otherwise we get the following error:

	Meson encountered an error in file overlay/meson.build, line 62, column 1:
	Unknown function "warning".

Fixes: 865a47ca ("overlay: parse tracepoints from sysfs to figure out fields' location")
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rhys Kidd <rhyskidd@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Petri Latvala <petri.latvala@intel.com>
Reviewed-by: Rhys Kidd <rhyskidd@gmail.com>
1 file changed