feat: improved detection whether a string requires all matches (#2167)

String sets like ($s*) always removed the STRING_FLAGS_SINGLE_MATCH flag, but only some operators (e.g. 1 of ($s*) at 0) actually mandated this.

In practice, the most common use case of string sets is n of ($s*), which does not necessitate removing STRING_FLAGS_SINGLE_MATCH.

Add logic to the operators to only remove this flag where it is necessary.

Author: secDre4mer

libyara/compiler.c

@@ -1078,3 +1078,14 @@ YR_API char* yr_compiler_get_error_message(
 
   return buffer;
 }
+
+YR_API int yr_string_set_destroy(YR_STRING_SET string_set)
+{
+  YR_STRING_SET_ELEMENT* head = string_set.head;
+  while (head != NULL) {
+    YR_STRING_SET_ELEMENT* next_head = head->next;
+    yr_free(head);
+    head = next_head;
+  }
+  return ERROR_SUCCESS;
+}