Revert ".github/workflows: work around golang/go#51629"

This reverts commit 2a412ac9ee.

Updates #4194

Change-Id: I0098b66b71d20bea301ca79058c1cdd201237dd0
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

.github/workflows/go-generate-without-stringer.sh

@@ -1,18 +0,0 @@
-#!/usr/bin/env sh
-#
-# This is a temporary hack to work around
-# https://github.com/golang/go/issues/51629 , wherein the stringer
-# generator doesn't work with generics.
-#
-# This script is the equivalent of `go generate ./...`, except that it
-# only runs generate on packages that don't try to use stringer.
-
-set -e
-
-find . -name '*.go' | xargs grep -l go:generate | xargs -n1 dirname | sort -u | while read dir; do
-	if ! egrep "cmd/(stringer|cloner)" $dir/*.go; then
-		set -x
-		go generate -tags=hermetic $dir
-		set +x
-	fi
-done

.github/workflows/go_generate.yml

@@ -25,13 +25,14 @@ jobs:
           fetch-depth: 0
 
       - name: check 'go generate' is clean
-        # The shell script invocation below is a temporary hack for
-        # https://github.com/tailscale/tailscale/issues/4194. When
-        # that issue is fixed, replace its invocation with:
-        # go generate --tags=hermetic ./...
         run: |
-          set -e
+          if [[ "${{github.ref}}" == release-branch/* ]]
-          ./.github/workflows/go-generate-without-stringer.sh
+          then
+            pkgs=$(go list ./... | grep -v dnsfallback)
+          else
+            pkgs=$(go list ./... | grep -v dnsfallback)
+          fi
+          go generate $pkgs
           echo
           echo
           git diff --name-only --exit-code || (echo "The files above need updating. Please run 'go generate'."; exit 1)

net/dnsfallback/dnsfallback.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:generate go run update-dns-fallbacks.go
+
 // Package dnsfallback contains a DNS fallback mechanism
 // for starting up Tailscale when the system DNS is broken or otherwise unavailable.
 package dnsfallback

net/dnsfallback/generate.go

@@ -1,10 +0,0 @@
-// Copyright (c) 2022 Tailscale Inc & 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 !hermetic
-// +build !hermetic
-
-package dnsfallback
-
-//go:generate go run update-dns-fallbacks.go