To merge with gcc's copy of configure.ac we need to revert changes to
configure.ac in the following gcc commits:
dc832fb39fc0 2022-08-25
fc259b522c0f 2022-06-25
Then reapply configure.ac changes in binutils from these binutils
commits:
50ad1254d5 2021-01-09
bb368aad29 2022-03-11
e5f2f7d901 2022-07-26
2cac01e3ff 2022-09-26
Plus copy over gcc's config/ax_cxx_compile_stdcxx.m4, then regenerate
configure.
