CI: Use merge time for activity check

[cmuellner]

The activity check of the nightly release pipeline extracts the field 'commit.author.date' from the top commit to decide if commit was added in the last 24 hours. However, unless PRs are reviewed and merged within 24 hours this activity check will fail. Using the date of the merge instead leads to a more robust activity check.

To give a concrete example, here are the top lines of today's commit log:

{
  "sha": "a14abe3265ae8bd3ce463aefa4645bd376d08e5a",
  "node_id": "C_kwDOAWrbKtoAKGExNGFiZTMyNjVhZThiZDNjZTQ2M2FlZmE0NjQ1YmQzNzZkMDhlNWE",
  "commit": {
    "author": {
      "name": "Christoph Müllner",
      "email": "christoph.muellner@vrull.eu",
      "date": "2024-10-12T22:54:57Z"
    },
    "committer": {
      "name": "Christoph Müllner",
      "email": "christophm30@gmail.com",
      "date": "2024-10-16T08:08:11Z"
    },
[...]

The existing code extracts the following time:

$ jq -r '.commit.author.date' commit.json
2024-10-12T22:54:57Z

The code change in this PR changes this to the following:

$ jq -r '.commit.committer.date' commit.json
2024-10-16T08:08:11Z

[cmuellner]

Background: I attempted to trigger a new nightly release. However, that failed because of the activity check. See https://github.com/riscv-collab/riscv-gnu-toolchain/actions/runs/11337056889/job/31636752315

[TommyMurphyTM1234]

The nightly build still seems to be failing to run so there still isn't a CI build of the GCC 14.2 based toolchain:

• https://github.com/riscv-collab/riscv-gnu-toolchain/issues/1569

Is that because this PR hasn't been merged yet or for some other reason?

[cmuellner]

The nightly build still seems to be failing to run so there still isn't a CI build of the GCC 14.2 based toolchain:

• Why is latest CI build still GCC 13.2 and not 14.2? #1569

Is that because this PR hasn't been merged yet or for some other reason?

Yes, the release builds are blocked because the activity check fails. This PR attempts to fix this.

[TommyMurphyTM1234]

Yes, the release builds are blocked because the activity check fails. This PR attempts to fix this.

OK - thanks @cmuellner. 👍

[cmuellner]

I'm merging this without a formal review from somebody else. This PR was available for several days and people are waiting for the CI/CD to work again.