ssh/tailssh: exclude Android from Linux build tags

As noted in #16048, the ./ssh/tailssh package failed to build on
Android, because GOOS=android also matches the "linux" build
tag. Exclude Android like iOS is excluded from macOS (darwin).

This now works:

    $ GOOS=android go install ./ipn/ipnlocal ./ssh/tailssh

The original PR at #16048 is also fine, but this stops the problem
earlier.

Updates #16048

Change-Id: Ie4a6f6966a012e510c9cb11dd0d1fa88c48fac37
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

.github/workflows/test.yml

@@ -305,7 +305,7 @@ jobs:
     - name: checkout
       uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - name: build some
-      run: ./tool/go build ./ipn/... ./wgengine/ ./types/... ./control/controlclient
+      run: ./tool/go build ./ipn/... ./ssh/tailssh ./wgengine/ ./types/... ./control/controlclient
       env:
         GOOS: ios
         GOARCH: arm64
@@ -375,7 +375,7 @@ jobs:
       # some Android breakages early.
       # TODO(bradfitz): better; see https://github.com/tailscale/tailscale/issues/4482
     - name: build some
-      run: ./tool/go install ./net/netns ./ipn/ipnlocal ./wgengine/magicsock/ ./wgengine/ ./wgengine/router/ ./wgengine/netstack ./util/dnsname/ ./ipn/ ./net/netmon ./wgengine/router/ ./tailcfg/ ./types/logger/ ./net/dns ./hostinfo ./version
+      run: ./tool/go install ./net/netns ./ipn/ipnlocal ./wgengine/magicsock/ ./wgengine/ ./wgengine/router/ ./wgengine/netstack ./util/dnsname/ ./ipn/ ./net/netmon ./wgengine/router/ ./tailcfg/ ./types/logger/ ./net/dns ./hostinfo ./version ./ssh/tailssh
       env:
         GOOS: android
         GOARCH: arm64

ssh/tailssh/incubator.go

@@ -7,7 +7,7 @@
 // and groups to the specified `--uid`, `--gid` and `--groups`, and
 // then launches the requested `--cmd`.
 
-//go:build linux || (darwin && !ios) || freebsd || openbsd
+//go:build (linux && !android) || (darwin && !ios) || freebsd || openbsd
 
 package tailssh
 

ssh/tailssh/incubator_linux.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux
+//go:build linux && !android
 
 package tailssh
 

ssh/tailssh/tailssh.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux || (darwin && !ios) || freebsd || openbsd || plan9
+//go:build (linux && !android) || (darwin && !ios) || freebsd || openbsd || plan9
 
 // Package tailssh is an SSH server integrated into Tailscale.
 package tailssh

ssh/tailssh/user.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux || (darwin && !ios) || freebsd || openbsd || plan9
+//go:build (linux && !android) || (darwin && !ios) || freebsd || openbsd || plan9
 
 package tailssh