new spack install of clingo may cause error

[white238]

per @adrienbernede

spack installs clingo in ~/.spack, and does that with spack-like install tree, coming with a database.
That would be OK if clingo was installed once for all, and the database version never changes.
There was a recent change in Spack, and all databases moved from yaml to json.
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This means, between two projects using a different version of spack, you may have a nice error because of a conflict on your database version in ~/.spack.
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Work around 1: (and typically a new feature for Uberenv): always set the store location (bootstrap clingo install) to a custom location. That may be a bit painful because installing clingo is painful.

Work around 2: Have LC install a clingo we can use. (We may still need work around 1, just to be safe)