[Bug libstdc++/90361] [9/10 Regression] Undefined symbols in libstdc++ when building with --with-default-libstdcxx-abi=gcc4-compatible

[ostash at ostash dot kiev.ua]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90361

--- Comment #6 from Viktor Ostashevskyi <ostash at ostash dot kiev.ua> ---
(In reply to Viktor Ostashevskyi from comment #5)
> It would be nice at least document that for GCC 9.1.0 building with
> --with-default-libstdcxx-abi=gcc4-compatible is broken.
> 
> Possible workaround is to build with default parameters and change
> _GLIBCXX_USE_DUAL_ABI define to 1 in bits/c++config.h after 'make install'.

s/_GLIBCXX_USE_DUAL_ABI define to 1/_GLIBCXX_USE_CXX11_ABI define to 0/