toolrunner should which tool before invoking (#220)

packages/exec/__tests__/scripts/print-args-sh.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# store arguments in a special array
+args=("$@")
+# get number of elements
+ELEMENTS=${#args[@]}
+
+# echo each element
+for (( i=0;i<$ELEMENTS;i++)); do
+    echo "args[$i]: \"${args[${i}]}\""
+done