stdatomic.h is a C++23 feature [1]. Thus, "older" compilers such as
gcc-11 (default in Ubuntu 22) do not know this, and can therefore not
correctly compile spsc_q. Fix this by alternatively including atomic for
C++.
Fixes errors such as
stdatomic.h:40:9: error: ‘_Atomic’ does not name a type
[1] https://en.cppreference.com/cpp/header/stdatomic.h
Signed-off-by: Robert Schmidt <robert.schmidt@openairinterface.org>
Robert Schmidt
74bc9bf0cc