platform-ci: Cancel current running CI on new push

This commit adds a concurrency group to the github workflow based on the
github ref. with `cancel-in-progres: true`, a push to a branch to github
will result in any previous instance of this workflow running for for
this being canceled.

Author: Javagedes

.github/workflows/platform-ci.yml

@@ -16,6 +16,10 @@ on:
     branches:
       - main
 
+concurrency:
+  group: "platform-ci-${{ github.ref }}"
+  cancel-in-progress: true
+
 jobs:
 
   # A job to produce the environment constants for this repository, so that the build job can