Add a test to check verification failure

jbmc/regression/jbmc-strings/IndexOfConstantEvaluation06-AssertionFailure/Main.java

@@ -0,0 +1,7 @@
+public class Main {
+
+  public void constantIndexOf() {
+    String s1 = "abcabc";
+    assert s1.indexOf("") == -1;
+  }
+}

jbmc/regression/jbmc-strings/IndexOfConstantEvaluation06-AssertionFailure/test.desc

@@ -0,0 +1,9 @@
+CORE symex-driven-lazy-loading-expected-failure
+Main.class
+--function Main.constantIndexOf --property "java::Main.constantIndexOf:()V.assertion.1"
+^Generated [0-9]+ VCC\(s\), 1 remaining after simplification$
+^VERIFICATION FAILED$
+^EXIT=10$
+^SIGNAL=0$
+--
+--