Fix the examples target info messaging (#1676)
Fix the examples target info messaging (#1676)

The echo for the target was copied from other targets that use `dir` as
an iteration variable which is not what this target uses. That means
that the empty variable `dir` is unexpanded and the unhelpful message of
"build /..." is echoed. This updates the iteration variable to match
other targets and fixes the info messaging.
open-telemetry/opentelemetry-go,open-telemetry/opentelemetry-go