zstd: add test.sh for script wrappers without --version

zstdgrep and zstdless are shell script wrappers that do not output a
version string, so the generic CI version check fails for them. Add a
test.sh case that verifies they are present and executable instead.

Signed-off-by: Alexandru Ardelean <alex@shruggie.ro>

utils/zstd/test.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+
+case "$1" in
+	zstd)
+		# zstdgrep and zstdless are shell script wrappers; they do not output a version
+		[ -x /usr/bin/zstdgrep ] || exit 1
+		[ -x /usr/bin/zstdless ] || exit 1
+		;;
+esac