dockerfile: promote --parents flag from labs

[jsternberg]

No description provided.

[tonistiigi]

I don't think this would be the right place for such fix. General rule is that LLB layer should have all the paths already in unix-style. If the client is working with Windows paths, then they convert them to Unix before LLB marshal, and if the wcow daemon needs a Windows path for local file operations, then they convert it from Unix to the local format.

cc @profnandaa

[jsternberg]

Doesn't seem to have worked anyway.

[jsternberg]

Switching this to draft until I fix the windows test. It appears we didn't run the labs tests on windows so this popped up here instead.

wcow failing

[jsternberg]

I made changes for normalizing the file path but when I attempted to update the integration test to work on Windows I didn't find any other examples of writing a windows command prompt test in such a way so I marked it as skipped for now. Similar tests were also skipped on Windows.

[tonistiigi]

cc @rzlink

[jsternberg]

@profnandaa @rzlink I'm having some issues trying to get a windows version of this test working. I'm getting this error: a decent amount

  sandbox.go:205: time="2025-10-31T15:22:45Z" level=error msg="/moby.buildkit.v1.Control/Solve returned error: rpc error: code = Unknown desc = failed to read C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\buildkit-mount2968917312\\System Volume Information: open \\System Volume Information: Access is denied." spanID=0140e0b624168def traceID=aa3abf39e6dd9193c5ae270a8c9129d9
    sandbox.go:205: failed to read C:\Users\RUNNER~1\AppData\Local\Temp\buildkit-mount2968917312\System Volume Information: open \System Volume Information: Access is denied.

I assumed it had something to do with the container user so I tried changing the user to ContainerAdministrator in all of the stages. I also tried getting rid of any heredoc lines from the test. I was curious if one of you two could take a look at the test and identify what I might be doing wrong.