docs: guide - empty buildkit cache doc

Signed-off-by: guillaume <guillaume.derouville@gmail.com>

docs/guides/1227-empty-buildkit-cache.md

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+---
+slug: /1227/empty-buildkit-cache
+displayed_sidebar: europa
+---
+
+# How to empty BuildKit's cache ?
+
+There are two ways of emptying the BuildKit cache:
+
+- Run your action with the `--no-cache` option:
+
+```console
+dagger do <your-action> --no-cache
+```
+
+- Stop and remove the buildkitd container and remove its associated volume:
+
+```console
+docker stop dagger-buildkitd ; docker rm dagger-buildkitd ; docker volume rm dagger-buildkitd
+```
+
+In 99.9% of the cases, the first solution is enough