Add pledge(2) support (OpenBSD only) via a 'protector' package. (#1297)

main.go

 package main
 
-import "github.com/junegunn/fzf/src"
+import (
+	"github.com/junegunn/fzf/src"
+	"github.com/junegunn/fzf/src/protector"
+)
 
 var revision string
 
 func main() {
+	protector.Protect()
 	fzf.Run(fzf.ParseOptions(), revision)
 }

src/protector/protector.go

+// +build !openbsd
+
+package protector
+
+// Protect calls OS specific protections like pledge on OpenBSD
+func Protect() {
+	return
+}

src/protector/protector_openbsd.go

+// +build openbsd
+
+package protector
+
+import "golang.org/x/sys/unix"
+
+// Protect calls OS specific protections like pledge on OpenBSD
+func Protect() {
+	unix.PledgePromises("stdio rpath tty proc exec")
+}