Until now, something like "guix build sed -v1 --check" would not get a
'build-succeeded' event, which in turn meant that the spinner would not
be erased upon build completion.
* nix/libstore/build.cc (DerivationGoal::registerOutputs): When
'buildMode' is bmCheck and 'settings.printBuildTrace' emit a
"@ build-succeeded" trace upon success.
* tests/store.scm ("build-succeeded trace in check mode"): New test.
d591242808