scripts: drop use of test -v
This is only available on Bash versions >= 4.2, which is (in
particular) not available by default on OS X.
@@ -50,7 +50,7 @@ Either the -a APPLICATION or the -e EXAMPLE option is required.
esac
done
-if [[ -v EXAMPLE ]]; then
+if [[ -n ${EXAMPLE+x} ]]; then
# Determine expected configuration file from example name and language variant.
case "${language}" in
rust)
