Auto merge of #1485 - semarie:openbsd-utime, r=gnzlbg
Auto merge of #1485 - semarie:openbsd-utime, r=gnzlbg

UTIME_OMIT and UTIME_NOW values are inverted on OpenBSD. correct it

unbreak OpenBSD after #1474

rust-lang/libc,rust-lang/libc,rust-lang/libc