[Chapel Merge] Serialize runs of `build-CI-container` workflow

Branch: refs/heads/main
Revision: 452e36162aa35904b1a269acf4d8bf78cdf8578e
Author: arifthpe
Link: Serialize runs of `build-CI-container` workflow by arifthpe · Pull Request #29079 · chapel-lang/chapel · GitHub
Log Message:
Serialize runs of build-CI-container workflow (#29079)

Serialize runs of the build-CI-container workflow, to prevent older
builds from racing and potentially overwriting the results of newer
builds.

This concurrency block should serialize all runs of this workflow on
main, queuing up new ones as they come in. See
https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#concurrency.

[reviewed by @jabraham17 , thanks!]

Compare: Comparing e40381d54ec79a4848876e71ab7a948014ef1b72...f430d162ffbd8a3aaab650e0710e484ea3f45631 · chapel-lang/chapel · GitHub

Diff:
M .github/workflows/build-CI-container.yml
https://github.com/chapel-lang/chapel/pull/29079.diff