[Bug c++/95700] read-md.c: "missing sentinel in function call" when building gcc with musl

[iii at linux dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95700

--- Comment #16 from Ilya Leoshkevich <iii at linux dot ibm.com> ---
I finally managed to reproduce this by doing `./configure
--host=aarch64-none-linux-gnu` on gcc113. The problem is that `CXX_FOR_BUILD`
doesn't seem to be set correctly - normally it's `g++-4.8.1 -std=gnu++11`, but
in this case it's just `g++`. I'm currently trying to wrap my head around
autotools build setup in order to figure out where exactly things went wrong.