Don't cache sandbox failures
Description
When building a project in BuildStream and there is a problem with the sandbox (for example, bwrap wasn't installed before running), the error will get cached and subsequent runs (after installing bwrap) will fail in the same way.
This behavior is counter intuitive and has already bitten multiple developers.
Changes proposed in this merge request:
- Don't cache sandbox failures
This merge request, when approved, will close: #727 (closed)
Edited by Benjamin Schubert