build failures due to 64-bit time_t on 32-bit systems (seen on Ubuntu 24.04 32bit) about frr HOT 2 OPEN

• atomic operations on time_t need libatomic because several 32bit platforms do not support 64bit atomic ops in the CPU

NB: this also means these operations will be slow as f*ck because they're emulated with a global lock for all atomic ops across the entire process

from frr.

All of these are due to Debian/Ubuntu changing time_t from 32bit to 64bit on all platforms. This means two things:

• time_t cannot be stored in a pointer, because it is larger than that
• atomic operations on time_t need libatomic because several 32bit platforms do not support 64bit atomic ops in the CPU
• time_t can never be printed directly with printf, because there is no format specifier for it. Both %ld and %lld are wrong. We could define a PRItime_t (like PRIu64) but honestly casting to (long long) and using %lld is simpler.

from frr.