fix: make `rustflags` optional for deserialization

[amrbashir]

closes #393

[github-actions[bot]]

Package Changes Through 7b1145c6ed7d60f41bd501ed501ad08623ee3017

There are 1 changes which include cargo-mobile2 with patch

Planned Package Versions

The following package releases are the planned based on the context of changes in this pull request. | package | current | next | |----|----|----| | cargo-mobile2 | 0.17.2 | 0.17.3 |

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