ci: Only try to push to s3 for same-repo pull requests (#110)

When running CI on pull requests, the S3 keys needed to push doc changes
are only accessible when the pull request comes from the same repo as
the project repo. If it is from a clone, these are not available, and
the push fails.

Work around this by correctly detecting this case, and avoiding the s3
push in these instances.

As we get more and more outside contributions, this will need to be
revisited, possibly with a separate workflow that runs in a different
context and has the keys available.

Author: d3zd3z

.github/workflows/docs.yml

@@ -81,7 +81,8 @@ jobs:
     runs-on: ubuntu-24.04
     if: |
       github.event_name == 'pull_request' &&
-      github.repository == 'zephyrproject-rtos/zephyr-lang-rust'
+      github.repository == 'zephyrproject-rtos/zephyr-lang-rust' &&
+      github.event.pull_request.repo.full_name == github.repository
 
     steps:
       - name: Download documentation artifact