[Bug bootstrap/70896] gcc4 ABI compatible bootstrap fails

[tulipawn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70896

--- Comment #3 from PeteVine <tulipawn at gmail dot com> ---
That option never caused me any troubles, btw. 

FWIW, once I've removed the `--disable-libstdcxx-dual-abi` option, the build
started chugging along quite nicely.