backends/backends: Add helpful message for getting rid of warning
@@ -284,7 +284,7 @@ class Backend:
if isinstance(t, build.CustomTarget):
if warn_multi_output and len(t.get_outputs()) != 1:
mlog.warning(f'custom_target {t.name!r} has more than one output! '
- 'Using the first one.')
+ f'Using the first one. Consider using `{t.name}[0]`.')
filename = t.get_outputs()[0]
elif isinstance(t, build.CustomTargetIndex):
filename = t.get_outputs()[0]
