Function openlane_config 

pub fn openlane_config(
    d: &DesignProfile,
    pdk: &PdkTarget,
    c: &ClosureSettings,
) -> String

Emit the OpenLane config.json for a design on a process.

The point of generating this rather than hand-writing it: a block cannot silently be built without the settings that were measured to be necessary, and the settings cannot drift from the evidence, because both live here and a lock reads them.