[Bug libffi/65726] [5/6 Regression] libffi fails to build when not bootstrapping: configure: error: C++ preprocessor "/lib/cpp" fails sanity check

[andreast at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65726

--- Comment #10 from Andreas Tobler <andreast at gcc dot gnu.org> ---
I will wait until gcc5 opens again and then I back-port this patch to gcc5 and
gcc49.