I've noticed some spurious failures in the lto tests (g++.dg/lto and gcc.dg/lto). They only occur with -jN. The symptom is an error message from ld complaining that a .lto.ltrans.o file is missing. I think this is a bug in the lto.exp script because the tests work fine with -j1.
I'll be taking a look to see if I can fix this. In the meantime, if you get weird errors, try running the failing tests cases with -j1. Thanks. Diego.