all: update build tags to require/assume Go 1.20

Updates #54265.

Change-Id: Ia1c9486484c73c565bb4f78234dedff6d929ed42
Reviewed-on: https://go-review.googlesource.com/c/go/+/511656
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

3 files changed, 5 insertions, 55 deletions

diff --git a/src/cmd/dist/exec_119.go b/src/cmd/dist/exec.go
index 0b4baa0065..602b812b00 100644
--- a/src/cmd/dist/exec_119.go
+++ b/src/cmd/dist/exec.go
@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.19
-// +build go1.19
-
 package main
 
 import (
diff --git a/src/cmd/dist/exec_118.go b/src/cmd/dist/exec_118.go
deleted file mode 100644
index a1c3c64d9e..0000000000
--- a/src/cmd/dist/exec_118.go
+++ /dev/null
@@ -1,47 +0,0 @@
-// Copyright 2021 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 !go1.19
-// +build !go1.19
-
-package main
-
-import (
-	"os"
-	"os/exec"
-	"strings"
-)
-
-// setDir sets cmd.Dir to dir, and also adds PWD=dir to cmd's environment.
-func setDir(cmd *exec.Cmd, dir string) {
-	cmd.Dir = dir
-	setEnv(cmd, "PWD", dir)
-}
-
-// setEnv sets cmd.Env so that key = value.
-func setEnv(cmd *exec.Cmd, key, value string) {
-	kv := key + "=" + value
-	if cmd.Env == nil {
-		cmd.Env = os.Environ()
-	}
-	cmd.Env = append(cmd.Env, kv)
-}
-
-// unsetEnv sets cmd.Env so that key is not present in the environment.
-func unsetEnv(cmd *exec.Cmd, key string) {
-	if cmd.Env == nil {
-		cmd.Env = os.Environ()
-	}
-
-	prefix := key + "="
-	newEnv := []string{}
-	for _, entry := range cmd.Env {
-		if strings.HasPrefix(entry, prefix) {
-			continue
-		}
-		newEnv = append(newEnv, entry)
-		// key may appear multiple times, so keep going.
-	}
-	cmd.Env = newEnv
-}
diff --git a/src/cmd/dist/notgo117.go b/src/cmd/dist/notgo120.go
index 8d551df24b..dd7657112f 100644
--- a/src/cmd/dist/notgo117.go
+++ b/src/cmd/dist/notgo120.go
@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Go 1.20 and later requires Go 1.17 as the bootstrap toolchain.
+// Go 1.22 and later requires Go 1.20 as the bootstrap toolchain.
 // If cmd/dist is built using an earlier Go version, this file will be
 // included in the build and cause an error like:
 //
 // % GOROOT_BOOTSTRAP=$HOME/sdk/go1.16 ./make.bash
 // Building Go cmd/dist using /Users/rsc/sdk/go1.16. (go1.16 darwin/amd64)
-// found packages main (build.go) and building_Go_requires_Go_1_17_13_or_later (notgo117.go) in /Users/rsc/go/src/cmd/dist
+// found packages main (build.go) and building_Go_requires_Go_1_20_6_or_later (notgo120.go) in /Users/rsc/go/src/cmd/dist
 // %
 //
 // which is the best we can do under the circumstances.
@@ -16,7 +16,7 @@
 // See go.dev/issue/44505 for more background on
 // why Go moved on from Go 1.4 for bootstrap.
 
-//go:build !go1.17
-// +build !go1.17
+//go:build !go1.20
+// +build !go1.20
 
-package building_Go_requires_Go_1_17_13_or_later
+package building_Go_requires_Go_1_20_6_or_later