mkfs -d is a feature that needs a stat() of the mkfs binary, which
often fails (as mkfs is often not invoked with a full path or from
the same directory). it makes setup look a bit messy as the error
is always printed while installing the system, for each created FS,
even though the situation is harmless. This change only complains
when the stat is actually needed (-d).
Change-Id: I54ac01505aa97c1cbe40456c04a35aed5a7ee953
fd5f2edf35