[tex-live] Install-TL (Win/32) conceals errors at first sight

[Karl Berry]

    Thanks, Karl : were you able to gain any
    insight(s) into how they came to be RO in
    the first place ?

At one point (long ago), I manually rebuilt those containers from a tree
that had the files as readonly.  I don't know how they got that way in
the first place and there's no way to trace it back farther at this
point.  We have added many checks to try to avoid it happening again.

karl