Segfaults on trying to load recursive external manifest file reference

[gasinvein]

Linux distribution and version

Fedora 34

Flatpak-builder version

1.1.1

Flatpak version

1.11.2

Description of the problem

Manifest can include other manifests from external files. If such manifest includes itself, flatpak-builder tries to load it, and segfaults. I believe recursive manifest reference should be explicitly prohibited.

Steps to reproduce

• Create a dummy module manifest file recursive-module.yml with this contents

  name: recursive-module
  buildsystem: simple
  build-commands: []
  modules:
    - recursive-module.yml
  

• Add a reference to this file to an app manifest modules
• Try to build the app