[Bug libgcc/67792] GCC 5.2 - make clean fails in libgcc

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67792

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Probably not fixed, just latent. Everyone just removes the whole build dir,
which works far more reliably.