Add timeout for Windows build steps

[mdickinson]

BPO	46203
Nosy	@mdickinson, @tiran, @zooba
PRs	bpo-46203: Add a (conservative) timeout for Windows builds on GitHub Actions #30301

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-01-09.10:30:13.160>
created_at = <Date 2021-12-30.11:06:59.921>
labels = ['3.11']
title = 'Add timeout for Windows build steps'
updated_at = <Date 2022-01-09.10:30:13.160>
user = 'https://github.com/mdickinson'

bugs.python.org fields:

activity = <Date 2022-01-09.10:30:13.160>
actor = 'mark.dickinson'
assignee = 'none'
closed = True
closed_date = <Date 2022-01-09.10:30:13.160>
closer = 'mark.dickinson'
components = []
creation = <Date 2021-12-30.11:06:59.921>
creator = 'mark.dickinson'
dependencies = []
files = []
hgrepos = []
issue_num = 46203
keywords = ['patch']
message_count = 1.0
messages = ['409359']
nosy_count = 3.0
nosy_names = ['mark.dickinson', 'christian.heimes', 'steve.dower']
pr_nums = ['30301']
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue46203'
versions = ['Python 3.11']

[mdickinson]

Recently there was an upstream issue with GitHub Actions that caused the Windows build steps in build.yml to hang. No output for the step was displayed in the build logs until the entire job was eventually cancelled, after the default step timeout of 6 hours.

I don't know how to fix the "no output" problem, but we can mitigate the 6 hour wait by adding a timeout for the build step. Some external discussion suggested that a conservative timeout of 30 minutes would be appropriate; looking at recent PRs, the build usually completes in around 5 minutes.

The (soon-to-be-)attached PR adds that timeout.

Here's the log from one of the failed jobs: https://github.com/python/cpython/runs/4641823914?check_suite_focus=true (note that this link will probably eventually become invalid).

Here's the relevant GitHub incident: https://www.githubstatus.com/incidents/gh0vvxtlj5v7