fix: arm32 compilation

[reneca]

There is an issue for ARM32 where the time_t is a 32 bits instead of a 64 bits.
It lead to a compilation error.

This fix replace the i64 cast by a try_into and handle the error.

[oschijns]

This also fixes compilation for i686 targets.
I tested it with

cargo zigbuild --target i686-unknown-linux-gnu --features=openssl-vendored

And the generated cargo-prosa binary also run successfully on a x86_64 Linux OS.