diff --git a/unum/vendor/golang.org/x/sys/unix/mkpost.go b/unum/vendor/golang.org/x/sys/unix/mkpost.go
new file mode 100644
index 0000000..d3ff659
--- /dev/null
+++ b/unum/vendor/golang.org/x/sys/unix/mkpost.go
@@ -0,0 +1,88 @@
+// Copyright 2016 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.
+
+// +build ignore
+
+// mkpost processes the output of cgo -godefs to
+// modify the generated types. It is used to clean up
+// the sys API in an architecture specific manner.
+//
+// mkpost is run after cgo -godefs; see README.md.
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"io/ioutil"
+	"log"
+	"os"
+	"regexp"
+)
+
+func main() {
+	// Get the OS and architecture (using GOARCH_TARGET if it exists)
+	goos := os.Getenv("GOOS")
+	goarch := os.Getenv("GOARCH_TARGET")
+	if goarch == "" {
+		goarch = os.Getenv("GOARCH")
+	}
+	// Check that we are using the new build system if we should be.
+	if goos == "linux" && goarch != "sparc64" {
+		if os.Getenv("GOLANG_SYS_BUILD") != "docker" {
+			os.Stderr.WriteString("In the new build system, mkpost should not be called directly.\n")
+			os.Stderr.WriteString("See README.md\n")
+			os.Exit(1)
+		}
+	}
+
+	b, err := ioutil.ReadAll(os.Stdin)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// If we have empty Ptrace structs, we should delete them. Only s390x emits
+	// nonempty Ptrace structs.
+	ptraceRexexp := regexp.MustCompile(`type Ptrace((Psw|Fpregs|Per) struct {\s*})`)
+	b = ptraceRexexp.ReplaceAll(b, nil)
+
+	// Replace the control_regs union with a blank identifier for now.
+	controlRegsRegex := regexp.MustCompile(`(Control_regs)\s+\[0\]uint64`)
+	b = controlRegsRegex.ReplaceAll(b, []byte("_ [0]uint64"))
+
+	// Remove fields that are added by glibc
+	// Note that this is unstable as the identifers are private.
+	removeFieldsRegex := regexp.MustCompile(`X__glibc\S*`)
+	b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
+
+	// We refuse to export private fields on s390x
+	if goarch == "s390x" && goos == "linux" {
+		// Remove cgo padding fields
+		removeFieldsRegex := regexp.MustCompile(`Pad_cgo_\d+`)
+		b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
+
+		// Remove padding, hidden, or unused fields
+		removeFieldsRegex = regexp.MustCompile(`X_\S+`)
+		b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
+	}
+
+	// Remove the first line of warning from cgo
+	b = b[bytes.IndexByte(b, '\n')+1:]
+	// Modify the command in the header to include:
+	//  mkpost, our own warning, and a build tag.
+	replacement := fmt.Sprintf(`$1 | go run mkpost.go
+// Code generated by the command above; see README.md. DO NOT EDIT.
+
+// +build %s,%s`, goarch, goos)
+	cgoCommandRegex := regexp.MustCompile(`(cgo -godefs .*)`)
+	b = cgoCommandRegex.ReplaceAll(b, []byte(replacement))
+
+	// gofmt
+	b, err = format.Source(b)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	os.Stdout.Write(b)
+}