WIP: Opening a workspace with a cached build
Description
(Note this is currently based off of !786 (merged) until it lands in master)
Change the default behaviour of opening a workspace to checkout the elements cached buildtree, if available
Changes proposed in this merge request:
- Make the default behaviour of bst workspace open checkout the elements cached buildtree if available
- Add --no-cache option to open command to override the default behaviour, dropping back to source checkout
- Add workspacebuildtrees option to global user config, allowing the user to set to false to override default behaviour
- If buildtrees are to be used but are unavailable, inform the user and drop back to source checkout
This merge request, when approved, will close: #311