I am having this issue since a month or two, maybe three, since boostrap USE flag was removed (as a USE flag). I got the same error with sys-devel/gcc-4.6.3 for sure and maybe sys-devel/gcc-4.5.4.
At first, a few months ago, I got a headach with dev-libs/mpc-1.0 and the likes, so I did not want to spent days, after hours and hours, to just update my system.
I dropped updates next the last month because of major instability. And now, I was suprised first to get a smooth update for a third of my system dropping here and there a few incompatible package (do not want to get another headach with virtual/ffmpeg-9, gnuts-3 etc.). But remain the old gcc issue.
The weird stuff is that the build log does not give any help. Everything seem to go smoothly untill that error without any clue where to look at.
Steps to Reproduce:
1. emerge -DNu1 sys-devel/gcc
2. emake failed with bootstrap-lean
Created attachment 346860 [details]
Created attachment 346862 [details]
*** This bug has been marked as a duplicate of bug 444762 ***