Add test 56-witness/71-var_eq-str-invariant (issue #1722)

Author: sim642

tests/regression/56-witness/71-var_eq-str-invariant.c

@@ -0,0 +1,5 @@
+// CRAM PARAM: --set ana.activated[+] var_eq
+int main() {
+  char text = "foobar";
+  return 0;
+}

tests/regression/56-witness/71-var_eq-str-invariant.t

@@ -0,0 +1,25 @@
+  $ goblint --set ana.activated[+] var_eq --enable witness.yaml.enabled --enable witness.invariant.other 71-var_eq-str-invariant.c
+  [Info][Deadcode] Logical lines of code (LLoC) summary:
+    live: 3
+    dead: 0
+    total lines: 3
+  [Info][Witness] witness generation summary:
+    location invariants: 1
+    loop invariants: 0
+    flow-insensitive invariants: 0
+    total generation entries: 1
+
+Should not contain invariant with string literal equality:
+
+  $ yamlWitnessStrip < witness.yml
+  - entry_type: invariant_set
+    content:
+    - invariant:
+        type: location_invariant
+        location:
+          file_name: 71-var_eq-str-invariant.c
+          line: 4
+          column: 3
+          function: main
+        value: '"foobar" == text'
+        format: c_expression