patch applied (testsuite): fix intermittent failure with ghci025

[Claus Reinke]

>  * fix intermittent failure with ghci025
> 
>    M ./tests/ghc-regress/ghci/scripts/ghci025.script +2

    -- ToDo: this will go wrong in parallel
    :! cp ../prog001/D1.hs ../prog001/D.hs

wouldn't it be easier to enforce the invariant that prog001/* 
is always compilable? ie, instead of having to create a D.hs
when needed, always have a D.hs, and just overwrite it
with D[12].hs as needed. that should work in parallel as
well because ghci025 only looks at the types, which don't 
change.

alternatively, it might be useful if scripts could create 
or copy the modules they need on the fly (some already 
do, i think, but there should be script-specific temporary
directories to put source in and to load source from,
to avoid interference, to simplify cleaning, and to
take 'in_testdir(.)' into account?).

thanks,
claus