…: 0xe: operation not permitted`

The error is known to happen when buildkitd is executed inside a
container without `--oci-worker-no-process-sandbox`.

Signed-off-by: Akihiro Suda <[email protected]>
(cherry picked from commit 591478d)
Signed-off-by: Akihiro Suda <[email protected]>

We can't avoid squashing even after just fixing up whiteout timestamps;
Squashing is still needed to apply the `touch`-ed timestamps across multiple `RUN` instructions.

Squashing will no longer be needed if we can merge PR 3560.

Signed-off-by: Akihiro Suda <[email protected]>
(cherry picked from commit 0758355)
Signed-off-by: Akihiro Suda <[email protected]>

ADD --checksum and git url graduated in v1.6,
removing the references to labs channel since
they are now in stable.

Signed-off-by: David Karlsson <[email protected]>
(cherry picked from commit dcc83f8)
Signed-off-by: Akihiro Suda <[email protected]>

[0.12 backport] docs: removed labs ref for ADD checksum and git

[0.12 backport] docs: troubleshoot for `mount proc:/proc (via /proc/self/fd/6), flags...

[0.12 backport] docs/build-repro.md: fix description about squashing

Signed-off-by: CrazyMax <[email protected]>
(cherry picked from commit 5b8f962)

[0.12 backport] filesync: write closer err discarded

`MultiWriter` would create an unnecessary map allocation when the
`Write` method was used. The `Write` method would create a progress
object with the meta field initialized to the meta field of the writer
itself. It then invoked its own `WriteRawProgress` method which would
see two maps with the metadata and erroneously believe that they were
different and needed to be merged into a single metadata map.

Since this map is initialized with the metadata of the writer before
`WriteRawProgress` is invoked, this merge was unnecessary and could add
a lot of unnecessary memory allocations during a build.

This changes the `MultiWriter.Write` method to invoke the private
`writeRawProgress` which performs the actual write and avoids the
metadata merge.

Signed-off-by: Jonathan A. Sternberg <[email protected]>
(cherry picked from commit 4c83fcf)

Instead of available space.

Signed-off-by: Justin Chadwell <[email protected]>
(cherry picked from commit a6e42ec)

Signed-off-by: Justin Chadwell <[email protected]>
(cherry picked from commit 49c848e)

[v0.12] v0.12.2 cherry-picks