icinga-build-deb|rpm-test: Fix positional argument detection

icinga-build-deb-test

@@ -20,7 +20,7 @@ fi
 )
 
 test_script=
-if [ -n "$@" ]; then
+if [ "$#" -gt 0 ]; then
   test_script="$@"
 elif [ -f "${ICINGA_BUILD_DEB_FLAVOR}/debian/icinga-build-test" ]; then
   test_script="${ICINGA_BUILD_DEB_FLAVOR}/debian/icinga-build-test"

icinga-build-rpm-test

@@ -57,7 +57,7 @@ REPO
 esac
 
 test_script=
-if [ -n "$@" ]; then
+if [ "$#" -gt 0 ]; then
   test_script="$@"
 elif [ -f "icinga-build-test" ]; then
   test_script="./icinga-build-test"