Ruby: Add barrier guards test involving captured variables

Author: hvitved

ruby/ql/test/library-tests/dataflow/barrier-guards/barrier-guards.rb

@@ -38,4 +38,27 @@
     foo
 else
     foo
-end
+end
+
+if foo == "foo"
+    capture {
+        foo # guarded
+    }
+end
+
+if foo == "foo"
+    capture {
+        foo = "bar"
+        foo # not guarded
+    }
+end
+
+if foo == "foo"
+    my_lambda = -> () {
+        foo # not guarded
+    }
+
+    foo = "bar"
+
+    my_lambda()
+end