GH-7397: Handle symlinked Dockerfiles

[Code0x58]

Resolves #7397

[thaJeztah]

Thanks! Looking at my steps trying to reproduce the problem (see #7397 (comment)), I'm actually wondering if this should be fixed in docker-compose; I'm thinking this should be fixed in the docker cli (or in buildkit), and docker-compose should pass the dockerfile path as-is (leaving the handling to the CLI)

[Code0x58]

Nice drill-down! I like the idea of it being cleaned up and handled in the CLI, it sounds like it could touch a lot of complements - I'm certainly interested to see how it's managed.

I'm wondering if this PR would find it's way in as a workaround at the docker-compose level, until changes are made to the CLI (and python library?), then here would need updating again.

[glours]

Thanks for taking the time to create this issue/pull request!

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