httpdate: favor gettimeofday(2) over time(2) for correctness
While scanning the git@vger.kernel.org mailing list, I've
learned time(2) may return the wrong value in the first 1 to 2.5
ms of every second. While I'm not sure if the Date: response
header matters to anyone, returning the correct time seems
prudent.
Link: https://lore.kernel.org/git/20230320230507.3932018-1-gitster@pobox.com/
Link: https://inbox.sourceware.org/libc-alpha/20230306160321.2942372-1-adhemerval.zanella@linaro.org/T/
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=30200