syscall: add utimensat and use it for UtimesNano on BSD and Solaris

All the BSDs and Solaris support the utimensat syscall, but Darwin
doesn't. Account for that by adding the //sys lines not to
syscall_bsd.go but the individual OS's syscall_*.go files and implement
utimensat on Darwin as just returning ENOSYS, such that UtimesNano will
fall back to use utimes as it currently does unconditionally.

This also adds the previously missing utimensat syscall number for
FreeBSD and Dragonfly.

Fixes #16480

Change-Id: I367454c6168eb1f7150b988fa16cf02abff42f34
Reviewed-on: https://go-review.googlesource.com/55130
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/syscall/zsyscall_freebsd_386.go b/src/syscall/zsyscall_freebsd_386.go
index 63061b2794..55fead990a 100644
--- a/src/syscall/zsyscall_freebsd_386.go
+++ b/src/syscall/zsyscall_freebsd_386.go
@@ -1308,3 +1308,18 @@ func accept4(fd int, rsa *RawSockaddrAny, addrlen *_Socklen, flags int) (nfd int
 	}
 	return
 }
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func utimensat(dirfd int, path string, times *[2]Timespec) (err error) {
+	var _p0 *byte
+	_p0, err = BytePtrFromString(path)
+	if err != nil {
+		return
+	}
+	_, _, e1 := Syscall(SYS_UTIMENSAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(times)))
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}