implemented pledge and unveil on openbsd

vendor/golang.org/x/sys/cpu/cpu_arm64.go

@@ -6,7 +6,10 @@ package cpu
 
 import "runtime"
 
-const cacheLineSize = 64
+// cacheLineSize is used to prevent false sharing of cache lines.
+// We choose 128 because Apple Silicon, a.k.a. M1, has 128-byte cache line size.
+// It doesn't cost much and is much more future-proof.
+const cacheLineSize = 128
 
 func initOptions() {
 	options = []option{
@@ -41,13 +44,10 @@ func archInit() {
 	switch runtime.GOOS {
 	case "freebsd":
 		readARM64Registers()
-	case "linux", "netbsd":
+	case "linux", "netbsd", "openbsd":
 		doinit()
 	default:
-		// Most platforms don't seem to allow reading these registers.
-		//
-		// OpenBSD:
-		// See https://golang.org/issue/31746
+		// Many platforms don't seem to allow reading these registers.
 		setMinimalFeatures()
 	}
 }