Emerging gcc-3.1-r4 installs two dead links: /usr/lib/gcc-lib/i686-pc-linux-gnu/3.1/libgcjgc.a and /usr/lib/gcc-lib/i686-pc-linux-gnu/3.1/libobjc_gc.a are both dead because the respective files in /usr/lib do not exist. Someone on IRC confirmed this error. I have bootstrapped with gcc 3.1 so I can't say if this error happens when having the multiversion of gcc 3.1 installed. Cheers
BTW, this bug is still in sys-devel/gcc-3.1-r6 after installing Gentoo via the Gentoo version 1.3a stage1 file.
fixed in later ebuilds