go.toolchain.rev, version: bump Tailscale Go, add IsTailscaleGo

Reports whether the current binary was built with Tailscale's
custom Go toolchain (the "tailscale_go" build tag).

For https://github.com/tailscale/go/pull/165

Updates tailscale/corp#39430

Change-Id: Ica437582ddf55d7df48b1453bad03ce14b1c0949
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

go.toolchain.next.rev

@@ -1 +1 @@
-f4de14a515221e27c0d79446b423849a6546e3a6
+179b46cade24e44f53b53a3cbcc7b7eb78469c31

go.toolchain.rev

@@ -1 +1 @@
-f4de14a515221e27c0d79446b423849a6546e3a6
+179b46cade24e44f53b53a3cbcc7b7eb78469c31

go.toolchain.rev.sri

@@ -1 +1 @@
-sha256-qmX68/Ml/jvf+sD9qykdx9QhSbkYaF8xJMFtd3iLHI8=
+sha256-VH+AgB1qjopwiB4w2SHrJm61O6yAl5ZaCGaDYnzb03o=

version/version.go

@@ -172,6 +172,10 @@ func majorMinorPatch() string {
 	return ret
 }
 
+// IsTailscaleGo reports whether the current binary was built with
+// Tailscale's custom Go toolchain.
+func IsTailscaleGo() bool { return isTailscaleGo }
+
 func isValidLongWithTwoRepos(v string) bool {
 	s := strings.Split(v, "-")
 	if len(s) != 3 {

version/version_not_tsgo.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !tailscale_go
+
+package version
+
+const isTailscaleGo = false

version/version_tsgo.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build tailscale_go
+
+package version
+
+const isTailscaleGo = true