/usr/src/gcc-4.6/debian/g++-BV-spu.overrides is in gcc-4.6-source 4.6.4-6ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | g++-@BV@-spu: non-standard-dir-in-usr usr/spu/
g++-@BV@-spu: file-in-unusual-dir
|