Fix TreeBuilder processing of zero-length array

TreeBuilder did not consider a zero-length array like a container and
never read the array's sizeof stored in the data buffer, leading to a
mismatch between bytes written vs read out of the buffer.

Now, `TreeBuilder::isContainer` does consider zero-length array like
a container and properly consume all the object sizes in the buffer.

oi/TreeBuilder.cpp

@@ -378,9 +378,20 @@ uint64_t TreeBuilder::next() {
 }
 
 bool TreeBuilder::isContainer(const Variable& variable) {
-  return th->containerTypeMap.contains(variable.type) ||
+  if (th->containerTypeMap.contains(variable.type)) {
-         (drgn_type_kind(variable.type) == DRGN_TYPE_ARRAY &&
+    return true;
-          drgn_type_length(variable.type) > 0);
+  }
+
+  if (drgn_type_kind(variable.type) == DRGN_TYPE_ARRAY) {
+    /* CodeGen v1 does not consider zero-length array as containers,
+     * but CodeGen v2 does. This discrepancy is handled here.
+     * TODO: Cleanup this workaround once CodeGen v1 is gone. See #453
+     */
+    return config.features[Feature::TypeGraph] ||
+           drgn_type_length(variable.type) > 0;
+  }
+
+  return false;
 }
 
 bool TreeBuilder::isPrimitive(struct drgn_type* type) {