Cancel running CI jobs when new changes are pushed to a PR

The `group` expression ensures that the cancel-in-progress
behavior is to only cancel if a new commit is pushed to the PR for
which the job is running, not other PRs.

This is a fairly standard snippet, used also in CI jobs for NumPy
and other projects.

.github/workflows/loongarch64.yml

@@ -2,6 +2,10 @@ name: loongarch64 qemu test
 
 on: [push, pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   TEST:
     if: "github.repository == 'OpenMathLib/OpenBLAS'"