fix openbsd build by disabling fuse on openbsd

fixes #5334

fuse/ipns/ipns_test.go

-// +build !nofuse
+// +build !nofuse,!openbsd
 
 package ipns
 

fuse/ipns/ipns_unix.go

-// +build !nofuse
+// +build !nofuse,!openbsd
 
 // package fuse/ipns implements a fuse filesystem that interfaces
 // with ipns, the naming system for ipfs.

fuse/ipns/link_unix.go

-// +build !nofuse
+// +build !nofuse,!openbsd
 
 package ipns
 

fuse/mount/fuse.go

-// +build !nofuse
-// +build !windows
+// +build !nofuse,!windows,!openbsd
 
 package mount
 

fuse/node/mount_openbsd.go

+// +build !nofuse
+
+package node
+
+import (
+	"errors"
+
+	core "github.com/ipfs/go-ipfs/core"
+)
+
+func Mount(node *core.IpfsNode, fsdir, nsdir string) error {
+	return errors.New("FUSE not supported on OpenBSD. See #5334 (https://git.io/fjMuC).")
+}

fuse/node/mount_test.go

-// +build !nofuse
+// +build !openbsd,!nofuse
 
 package node
 

fuse/node/mount_unix.go

-// +build !windows,!nofuse
+// +build !windows,!openbsd,!nofuse
 
 package node
 

fuse/readonly/ipfs_test.go

-// +build !nofuse
+// +build !nofuse,!openbsd
 
 package readonly
 

fuse/readonly/mount_unix.go

-// +build linux darwin freebsd netbsd openbsd
+// +build linux darwin freebsd netbsd
 // +build !nofuse
 
 package readonly

fuse/readonly/readonly_unix.go

-// +build linux darwin freebsd netbsd openbsd
+// +build linux darwin freebsd netbsd
 // +build !nofuse
 
 package readonly

mk/util.mk

@@ -20,8 +20,12 @@ SUPPORTED_PLATFORMS += linux-amd64
 SUPPORTED_PLATFORMS += darwin-386
 SUPPORTED_PLATFORMS += darwin-amd64
 
+SUPPORTED_PLATFORMS += freebsd-386
 SUPPORTED_PLATFORMS += freebsd-amd64
 
+SUPPORTED_PLATFORMS += openbsd-386
+SUPPORTED_PLATFORMS += openbsd-amd64
+
 space:=
 space+=
 comma:=,