[Bug libstdc++/84568] libstdc++-v3 configure checks for atomic operations fail on riscv

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84568

--- Comment #4 from Andreas Schwab <schwab@linux-m68k.org> ---
Not having inline atomics already breaks so many things.