Add concurrency to the Key4hep workflows

Author: jmcarcell

.github/workflows/downstream-build.yaml

@@ -1,9 +1,16 @@
+# Do not edit this file, it will be overwritten!
+# The template file can be found in
+# https://github.com/key4hep/key4hep-actions/blob/main/workflows/downstream-build.yaml
 name: downstream-build
 
 on:
   pull_request:
   workflow_dispatch:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   downstream-build:
     runs-on: ubuntu-latest

.github/workflows/key4hep-build.yaml

@@ -12,6 +12,9 @@ on:
   schedule:
         - cron: '16 5 * * *'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   build: