Create StringSet DerivationBuilderParams::systemFeatures

Do this to avoid checking "system features" from the store config
directly, because we rather not have `DerivationBuilder` depend on
`Store`.

src/libstore/build/derivation-building-goal.cc

@@ -766,6 +766,7 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
                     .initialOutputs = initialOutputs,
                     .buildMode = buildMode,
                     .defaultPathsInChroot = std::move(defaultPathsInChroot),
+                    .systemFeatures = worker.store.config.systemFeatures.get(),
                     .finalEnv = std::move(finalEnv),
                     .extraFiles = std::move(extraFiles),
                 });