bug#6401:

[Glenn Morris <rgm@gnu.org>]

Eli Zaretskii wrote:

>> http://lists.gnu.org/archive/html/emacs-devel/2008-10/msg00432.html
>> 
>> I don't know if a solution was ever found for that.
>
> No solution was found, because I, like you, don't know what to do
> about it.  Emacs has no way of knowing whether EMACSDATA etc. is set
> for it or for some other Emacs.  So it cannot remove it from the
> environment when running subprocesses.  Maybe someone could come up
> with some clever idea.

If all else fails, we can at least write a PROBLEMS entry.
Why does a --with-ns build actually need to set these env-vars for child
processes?
Could they specifically be unset in spawned M-x shells?
Similar to the suggestion in emacs-devel, could configure unset
$EMACSDATA if $EMACS is set (which indicates it is running from an Emacs
shell)? Under what circusmtances would one want to set EMACSDATA when
building Emacs? Or could we replace the env-var with a --with-emacsdata
argument to configure instead? Then people who need the functionality
can still access it, and people who don't won't inadvertently get
affected by it.