diff --git a/tempfork/internal/testenv/testenv.go b/tempfork/internal/testenv/testenv.go
deleted file mode 100644
index 40a708f10..000000000
--- a/tempfork/internal/testenv/testenv.go
+++ /dev/null
@@ -1,160 +0,0 @@
-// Copyright 2015 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.
-
-// Package testenv is Tailscale's fork/subset of Go's
-// internal/testenv. It exists to satisfy the tests of our fork of
-// crypto/x509.
-package testenv
-
-import (
-	"errors"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"runtime"
-	"strings"
-	"testing"
-)
-
-// HasGoBuild reports whether the current system can build programs with ``go build''
-// and then run them with os.StartProcess or exec.Command.
-func HasGoBuild() bool {
-	if os.Getenv("GO_GCFLAGS") != "" {
-		// It's too much work to require every caller of the go command
-		// to pass along "-gcflags="+os.Getenv("GO_GCFLAGS").
-		// For now, if $GO_GCFLAGS is set, report that we simply can't
-		// run go build.
-		return false
-	}
-	switch runtime.GOOS {
-	case "android", "js":
-		return false
-	case "darwin":
-		if runtime.GOARCH == "arm64" {
-			return false
-		}
-	}
-	return true
-}
-
-// MustHaveGoBuild checks that the current system can build programs with ``go build''
-// and then run them with os.StartProcess or exec.Command.
-// If not, MustHaveGoBuild calls t.Skip with an explanation.
-func MustHaveGoBuild(t testing.TB) {
-	if os.Getenv("GO_GCFLAGS") != "" {
-		t.Skipf("skipping test: 'go build' not compatible with setting $GO_GCFLAGS")
-	}
-	if !HasGoBuild() {
-		t.Skipf("skipping test: 'go build' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
-	}
-}
-
-// HasGoRun reports whether the current system can run programs with ``go run.''
-func HasGoRun() bool {
-	// For now, having go run and having go build are the same.
-	return HasGoBuild()
-}
-
-// MustHaveGoRun checks that the current system can run programs with ``go run.''
-// If not, MustHaveGoRun calls t.Skip with an explanation.
-func MustHaveGoRun(t testing.TB) {
-	if !HasGoRun() {
-		t.Skipf("skipping test: 'go run' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
-	}
-}
-
-// GoTool reports the path to the Go tool.
-func GoTool() (string, error) {
-	if !HasGoBuild() {
-		return "", errors.New("platform cannot run go tool")
-	}
-	var exeSuffix string
-	if runtime.GOOS == "windows" {
-		exeSuffix = ".exe"
-	}
-	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
-	if _, err := os.Stat(path); err == nil {
-		return path, nil
-	}
-	goBin, err := exec.LookPath("go" + exeSuffix)
-	if err != nil {
-		return "", errors.New("cannot find go tool: " + err.Error())
-	}
-	return goBin, nil
-}
-
-// GoToolPath reports the path to the Go tool.
-// It is a convenience wrapper around GoTool.
-// If the tool is unavailable GoToolPath calls t.Skip.
-// If the tool should be available and isn't, GoToolPath calls t.Fatal.
-func GoToolPath(t testing.TB) string {
-	MustHaveGoBuild(t)
-	path, err := GoTool()
-	if err != nil {
-		t.Fatal(err)
-	}
-	// Add all environment variables that affect the Go command to test metadata.
-	// Cached test results will be invalidate when these variables change.
-	// See golang.org/issue/32285.
-	for _, envVar := range strings.Fields(KnownEnv) {
-		os.Getenv(envVar)
-	}
-	return path
-}
-
-// KnownEnv is a list of environment variables that affect the operation
-// of the Go command.
-const KnownEnv = `
-	AR
-	CC
-	CGO_CFLAGS
-	CGO_CFLAGS_ALLOW
-	CGO_CFLAGS_DISALLOW
-	CGO_CPPFLAGS
-	CGO_CPPFLAGS_ALLOW
-	CGO_CPPFLAGS_DISALLOW
-	CGO_CXXFLAGS
-	CGO_CXXFLAGS_ALLOW
-	CGO_CXXFLAGS_DISALLOW
-	CGO_ENABLED
-	CGO_FFLAGS
-	CGO_FFLAGS_ALLOW
-	CGO_FFLAGS_DISALLOW
-	CGO_LDFLAGS
-	CGO_LDFLAGS_ALLOW
-	CGO_LDFLAGS_DISALLOW
-	CXX
-	FC
-	GCCGO
-	GO111MODULE
-	GO386
-	GOARCH
-	GOARM
-	GOBIN
-	GOCACHE
-	GOENV
-	GOEXE
-	GOFLAGS
-	GOGCCFLAGS
-	GOHOSTARCH
-	GOHOSTOS
-	GOINSECURE
-	GOMIPS
-	GOMIPS64
-	GOMODCACHE
-	GONOPROXY
-	GONOSUMDB
-	GOOS
-	GOPATH
-	GOPPC64
-	GOPRIVATE
-	GOPROXY
-	GOROOT
-	GOSUMDB
-	GOTMPDIR
-	GOTOOLDIR
-	GOWASM
-	GO_EXTLINK_ENABLED
-	PKG_CONFIG
-`