In OneShot mode, Finder ignores hiDir settings when looking for HomeModule
When compiling in OneShot mode, the Finder only looks for interface files (*.hi) even for home module as can be seen here. The location making function used for these however, doesn't take into account the
hiDir field of the current
DynFlags of the session at all as can be seen here and here. This strikes me as incorrect and should be unintentional.