unix: update openbsd Statfs_t fields

This changes some fields of openbsd Statfs_t from arrays of int8
to arrays of byte. This makes the types of those fields correspond to
the types used on most other BSD systems (Darwin, FreeBSD, NetBSD),
and simplifies the conversion to Go string.

Similar changes: CL 359674, CL 259903, CL 74331.

Note that while this patches mkpost.go, the end result is obtained by
manual editing of ztypes_openbsd_*.go files. The reasons for this are:

1. automatic regeneration (tried on openbsd 6.9 / amd64) brings in way
   too many changes (5 files changed, 193 insertions, 45 deletions).

2. I could not figure out how to run openbsd on non-amd64.

Nevertheless, this change is sufficient, meaning if someone will
actually end up regenerating these (see e.g. CL 347649) after this
commit is merged, the fields will still be kept as arrays of byte.

Change-Id: I4520889f11f6ac2d9befe17c7a77186198c08cd2
Reviewed-on: https://go-review.googlesource.com/c/sys/+/407195
Run-TryBot: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: 谢致邦 <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Tobias Klauser <[email protected]>

Author: kolyshkin

unix/mkpost.go

@@ -101,9 +101,9 @@ func main() {
 	convertUtsnameRegex := regexp.MustCompile(`((Sys|Node|Domain)name|Release|Version|Machine)(\s+)\[(\d+)\]u?int8`)
 	b = convertUtsnameRegex.ReplaceAll(b, []byte("$1$3[$4]byte"))
 
-	// Convert [n]int8 to [n]byte in Statvfs_t members to simplify
+	// Convert [n]int8 to [n]byte in Statvfs_t and Statfs_t members to simplify
 	// conversion to string.
-	convertStatvfsRegex := regexp.MustCompile(`((Fstype|Mnton|Mntfrom)name)(\s+)\[(\d+)\]int8`)
+	convertStatvfsRegex := regexp.MustCompile(`(([Ff]stype|[Mm]nton|[Mm]ntfrom)name|mntfromspec)(\s+)\[(\d+)\]int8`)
 	b = convertStatvfsRegex.ReplaceAll(b, []byte("$1$3[$4]byte"))
 
 	// Convert []int8 to []byte in device mapper ioctl interface