This bug came to my attention when trying to build virtualbox in a setup using 
distcc.

Related reports are:
https://bugs.gentoo.org/show_bug.cgi?id=351979
https://bugs.gentoo.org/show_bug.cgi?id=306409

This lead me to:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=626926

There one can find a full analysis of the problem, along with a patch.

I'll attach the patch here for completeness; full credit goes to Jiri Palecek, 
the reporter of the above-mentioned debian bug.