x/build: add LUCI plan9-386 builder

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• Hostname: plan9-386
• Certificate Request: plan9-386.csr.txt

[cagedmantis]

@golang/release

[gopherbot]

Change https://go.dev/cl/536196 mentions this issue: main.star: add plan9-{386, amd64, arm} builders

[cagedmantis]

Here is the certificate: plan9-386-1698265768.cert.txt

[0intro]

Thank you for the certificate.

I've tried to launch the swarming bot, but I came across this error:

$ luci_machine_tokend -backend luci-token-server.appspot.com -cert-pem plan9-386.crt -pkey-pem plan9-386.key -token-file=$HOME/lib/luci_machine_tokend/token.json
[I2023-11-10T19:22:20.630093+01:00 822864 0 iface.go:167] tsmon is disabled because no endpoint is configured
[I2023-11-10T19:22:20.630912+01:00 822864 0 main.go:237] The token is valid, skipping the update

$ bootstrapswarm -token-file-path $HOME/lib/luci_machine_tokend/token.json -hostname plan9-386
2023/11/10 19:22:24 Bootstrapping the swarming bot with certificate authentication
2023/11/10 19:22:24 retrieving the luci-machine-token from the token file
2023/11/10 19:22:24 Downloading the swarming bot
2023/11/10 19:22:25 Starting the swarming bot /home/djc/.swarming/swarming_bot.zip
822925 2023-11-10 18:22:26.773 E: Request to https://chromium-swarm.appspot.com/swarming/api/v1/bot/handshake failed with HTTP status code 403: 403 Client Error: Forbidden for url: https://chromium-swarm.appspot.com/swarming/api/v1/bot/handshake
822925 2023-11-10 18:22:26.773 E: Failed to contact for handshake, retrying in 0 sec...

Is there something I'm doing wrong?

Also, since we can't run Python on Plan 9, the idea is to run the swarming bot on a Linux machine, which will run the command on a remote Plan 9 instance (like ssh glenda@plan9 ls /).
Can the swarming bot be used this way? Maybe there is a similar approach to run the Go tests on Android.

Thanks.

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CC @millerresearch