build: add support for OpenBSD

[anoduck]

Pebble is a requirement for httpx, and thus during installation it ejected the following set of errors, which immediately caused the installation to fail.:

# github.com/cockroachdb/pebble/vfs
/go/bin/pkg/mod/github.com/cockroachdb/pebble@v0.0.0-20230207164304-7d1e4ba7ffd0/vfs/disk_usage_unix.go:18:27: stat.Bsize undefined (type unix.Statfs_t has no field or method Bsize)
/go/bin/pkg/mod/github.com/cockroachdb/pebble@v0.0.0-20230207164304-7d1e4ba7ffd0/vfs/disk_usage_unix.go:18:48: stat.Bfree undefined (type unix.Statfs_t has no field or method Bfree)
/go/bin/pkg/mod/github.com/cockroachdb/pebble@v0.0.0-20230207164304-7d1e4ba7ffd0/vfs/disk_usage_unix.go:19:28: stat.Bsize undefined (type unix.Statfs_t has no field or method Bsize)
/go/bin/pkg/mod/github.com/cockroachdb/pebble@v0.0.0-20230207164304-7d1e4ba7ffd0/vfs/disk_usage_unix.go:19:49: stat.Bavail undefined (type unix.Statfs_t has no field or method Bavail)
/go/bin/pkg/mod/github.com/cockroachdb/pebble@v0.0.0-20230207164304-7d1e4ba7ffd0/vfs/disk_usage_unix.go:20:28: stat.Bsize undefined (type unix.Statfs_t has no field or method Bsize)
/go/bin/pkg/mod/github.com/cockroachdb/pebble@v0.0.0-20230207164304-7d1e4ba7ffd0/vfs/disk_usage_unix.go:20:49: stat.Blocks undefined (type unix.Statfs_t has no field or method Blocks)

System: OpenBSD Current 7.2
Go Version: go1.19.4 openbsd/amd64

Any information to further help diagnose the issue would be greatly appreciated.

Jira issue: PEBBLE-128

[nicktrav]

It looks like we don't currently support OpenBSD. However, we do support FreeBSD.

$ GOOS=openbsd go build -o /tmp/pebble ./cmd/pebble
# github.com/cockroachdb/pebble/vfs
vfs/disk_usage_unix.go:18:27: stat.Bsize undefined (type "golang.org/x/sys/unix".Statfs_t has no field or method Bsize)
vfs/disk_usage_unix.go:18:48: stat.Bfree undefined (type "golang.org/x/sys/unix".Statfs_t has no field or method Bfree)
vfs/disk_usage_unix.go:19:28: stat.Bsize undefined (type "golang.org/x/sys/unix".Statfs_t has no field or method Bsize)
vfs/disk_usage_unix.go:19:49: stat.Bavail undefined (type "golang.org/x/sys/unix".Statfs_t has no field or method Bavail)
vfs/disk_usage_unix.go:20:28: stat.Bsize undefined (type "golang.org/x/sys/unix".Statfs_t has no field or method Bsize)
vfs/disk_usage_unix.go:20:49: stat.Blocks undefined (type "golang.org/x/sys/unix".Statfs_t has no field or method Blocks)

$ GOOS=freebsd go build -o /tmp/pebble ./cmd/pebble && echo $?
0

Perhaps we should consider adding support. I'll repurpose this issue slightly to track that work. Thank you for raising!

[nicktrav]

Looks like on OpenBSD the field names are slightly different.

https://github.com/golang/sys/blob/4fee21c923398823434653737e3d413027fe4cdd/unix/ztypes_openbsd_amd64.go#L79-L103

This shouldn't be too hard to fix. We'll likely just need to add a disk_usage_openbsd.go.

[nicktrav]

We should also add a build target for this in our CI pipeline. Perhaps Free and OpenBSD could be part of a CI matrix.