Allow whck override with bin/whck or whck from env

otherwise explicit whck is not passed to test_web.sh which will try
to build from whck submodule

bin/test.sh

@@ -17,9 +17,18 @@ fi
 # If bin/server succeeds, it contains a path to the executable
 # Otherwise it may contain build error messages
 server="$("$BASEDIR"/bin/server)"
+
+# Try to detect a whck override
+if [ -f "$BASEDIR"/bin/whck ]; then
+    whck="$BASEDIR"/bin/whck
+elif which "whck"; then
+    whck="$(which "whck")"
+else
+    whck=""
+
 if [ $? -eq 0 ]; then
     # Let test_web.sh figure out the path to whck
-    "$BASEDIR"/spec/test_web.sh "$server"
+    "$BASEDIR"/spec/test_web.sh "$server" "$whck"
     status=$?
 else
     status=1