Compose elements with integration commands do not work on buildbox

Summary

A new test introduced by !1722 (merged) had to be marked as xfail on buildbox.

It fails with error:

[00:00:03][9b0012db][   build:compose/compose-amhello.bst   ] FAILURE Directory '/buildstream/install' was not found inside the sandbox, unable to collect artifact contents

See logs: https://gitlab.com/BuildStream/buildstream/-/jobs/356465941

Test is tests/integration/compose.py::test_compose_run_integration.

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