To work with more compilers without requiring separate libs to
link. Like with gcc-12 for RISC-V on Linux.
Reported-by: Adam Sampson
Fixes#9055Closes#9061
clang 14 warns about its use. It is being deprecated by the working
group for the programming language C: "The macro ATOMIC_VAR_INIT is
basically useless for the purpose for which it was designed"
Ref: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2886.htm
Reported-by: Tatsuhiro Tsujikawa
Fixes#9041Closes#9042
