ci: Bump centos gcc to 12

[maflcko]

Currently the centos stream9 CI task is using gcc-11. This is fine, because this is also the minimum supported.

However:

• There is already a CI task that is checking the minimum supported version:

  bitcoin/ci/test/00_setup_env_native_previous_releases.sh

  Lines 11 to 12 in 62bd61d

  	# Use minimum supported python3.10 and gcc-11, see doc/dependencies.md
  	export PACKAGES="gcc-11 g++-11 python3-zmq"

• The CI log is a bit useless, because it is mostly just #warning _FORTIFY_SOURCE > 2 is treated like 2 on this platform [-Werror=cpp]. This makes it harder to spot real warnings, such as CI: Cmake warnings should be errors #31476

Fix both issues by using gcc-12.

[DrahtBot]

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/31477.

Reviews

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Type	Reviewers
ACK	hebasto

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #31349 (ci: detect outbound internet traffic generated while running tests by vasild)
• #30997 (build: Switch to Qt 6 by hebasto)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[DrahtBot]

🚧 At least one of the CI tasks failed.
_{Debug: https://github.com/bitcoin/bitcoin/runs/34303618224}

Hints

Try to run the tests locally, according to the documentation. However, a CI failure may still
happen due to a number of reasons, for example:

• Possibly due to a silent merge conflict (the changes in this pull request being
  incompatible with the current code in the target branch). If so, make sure to rebase on the latest
  commit of the target branch.

• A sanitizer issue, which can only be found by compiling with the sanitizer and running the
  affected test.

• An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

[hebasto]

ACK fa47baa.