Some guarantee of how long the build root pathname can be on Windows is needed.

The current situation is that there obviously is some limit, but it changes
arbitrarily from milestone to milestone. For instance in ooo310-m18, using a
build root of length 43 ("c:/ooo/git/ooo-build-3-1-1/build/ooo310-m18") didn't work:

Error: -- error converting
"c:/ooo/git/ooo-build-3-1-1/build/ooo310-m18/sdext/source/minimizer/registry/data/org/openoffice/Office/extension/../../../../../../../../wntmsci12.pro/misc/PresentationMinimizer_in/registry/res/en-US/org/openoffice/Office/extension/SunPresentationMinimizer.xcu"
- File name too long

Now, you might say that c:\ooo\git\ooo-build-3-1-1\build\ooo310-m18 is
"obviously" too long and using something like that is just asking for trouble,
but hey, just two characters shorter worked fine for ooo310-m11.

When such a guarantee is given, the configure.in should then enforce that this
limit isn't exceeded, and it should also ideally be continuously verified that
using this length of build root pathname actually works, for instance in the
buildbots or whatever.

(Note that I am *not* asking for any guarantee that the specified limit actually
*is* the limit. I.e. it would just be the guaranteed lower limit for maximum
length.)

Once there is a guaranteed length that will work, it would be nice if this limit
could be gradually increased by doing work on reducing the redundancy in some
folder pathnames, and dropping pointless folder levels with just one subfolder.
But that is for another enhancement request then.