This fixes a bug noticed during ARM64 bringup where DHCP never completed. In dhcpoffer, `stop_selecting` is declared int (32-bit) but assigned two time_t operands of 64-bit.
The truncated value breaks the timeout, leaving DHCP stuck in S_SELECTING. This is masked on AMD64 because the RTC is implemented there and `time()` returns values that fit in 32 bits. On ARM64 the RTC isn't implemented yet, exposing the truncation.
CORE-18200
b3a0868a18