build: buildkit-root-volume-memory opt for kubernetes driver (#22865)

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## Description

Doc Update for change in buildx repo

## Related issues or tickets

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docker/buildx#3253

## Reviews

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- [ ] Technical review
- [ ] Editorial review
- [ ] Product review

---------

Signed-off-by: Samuel Archambault <samuel.archambault@getmaintainx.com>
Co-authored-by: Samuel Archambault <samuel.archambault@getmaintainx.com>
Co-authored-by: Allie Sadler <102604716+aevesdocker@users.noreply.github.com>

Author: 3 people

content/manuals/build/builders/drivers/kubernetes.md

@@ -42,6 +42,7 @@ can pass to `--driver-opt`:
 | `limits.cpu`                 | CPU units    |                                         | Sets the limit CPU value specified in units of Kubernetes CPU. For example `requests.cpu=100m` or `requests.cpu=2`                   |
 | `limits.memory`              | Memory size  |                                         | Sets the limit memory value specified in bytes or with a valid suffix. For example `requests.memory=500Mi` or `requests.memory=4G`   |
 | `limits.ephemeral-storage`   | Storage size |                                         | Sets the limit ephemeral-storage value specified in bytes or with a valid suffix. For example `requests.ephemeral-storage=100M`      |
+| `buildkit-root-volume-memory`| Memory size  | Using regular file system               | Mounts `/var/lib/buildkit` on an `emptyDir` memory-backed volume, with `SizeLimit` as the value. For example, `buildkit-root-folder-memory=6G`     |
 | `nodeselector`               | CSV string   |                                         | Sets the pod's `nodeSelector` label(s). See [node assignment][2].                                                                    |
 | `annotations`                | CSV string   |                                         | Sets additional annotations on the deployments and pods.                                                                             |
 | `labels`                     | CSV string   |                                         | Sets additional labels on the deployments and pods.                                                                                  |