[rules] Specify fusesoc cache dir to be in the bazel tree

[a-will]

Make the fusesoc cache dir be in the bazel tree, so fusesoc doesn't attempt to create directories outside, such as ~/.cache/fusesoc. That action can cause build failures, since fusesoc is sandboxed.

Fixes #23696

[a-will]

I think this would fix #22833 and a bug that @AlexJones0 was having. It LGTM, was there something you wanted to change before marking as ready?

It was merely marked draft because of the quiet period (since it changes something with tool flows, though it should represent a fix, hehe).

[a-will]

I've marked it ready, since the development is ostensibly done, but do check that the merge window for such changes is open before merging.

[github-actions[bot]]

Successfully created backport PR for earlgrey_1.0.0:

• #25364

[github-actions[bot]]

Successfully created backport PR for earlgrey_es_sival:

• #25382

[github-actions[bot]]

Backport failed for earlgrey_1.0.0, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin earlgrey_1.0.0
git worktree add -d .worktree/backport-23698-to-earlgrey_1.0.0 origin/earlgrey_1.0.0
cd .worktree/backport-23698-to-earlgrey_1.0.0
git switch --create backport-23698-to-earlgrey_1.0.0
git cherry-pick -x eb70af74ecfb70198038c28502e386aa9970e9c8