compiler: build separation runtime with clite

runtime/internal/lib/os/exec/unix_constants.go

@@ -0,0 +1,13 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix
+
+package exec
+
+const (
+	unix_R_OK = 0x4
+	unix_W_OK = 0x2
+	unix_X_OK = 0x1
+)