Add regression test to check verification failure

Author: yumibagge

jbmc/regression/jbmc-strings/ConstantEvaluationStringConcatenation05-VerificationFailure/Main.class

@@ -0,0 +1,15 @@
+public class Main {
+  public void test1() {
+    String s1 = "abc";
+    String s2 = "xyz";
+    String s3 = s1 + s2;
+    assert s3.length() == 7;
+  }
+
+  public void test2() {
+    String s1 = "abc";
+    String s2 = "xyz";
+    String s3 = s1 + s2;
+    assert s3.startsWith("abcdefg");
+  }
+}

jbmc/regression/jbmc-strings/ConstantEvaluationStringConcatenation05-VerificationFailure/Main.java

@@ -0,0 +1,8 @@
+CORE
+Main.class
+--function Main.test1
+^EXIT=10$
+^SIGNAL=0$
+^VERIFICATION FAILED$
+--
+--

jbmc/regression/jbmc-strings/ConstantEvaluationStringConcatenation05-VerificationFailure/test1.desc

@@ -0,0 +1,8 @@
+CORE
+Main.class
+--function Main.test2
+^EXIT=10$
+^SIGNAL=0$
+^VERIFICATION FAILED$
+--
+--