stop triggering on push to all branches, and only auto-trigger for de…

…fault PR activity types

.github/workflows/cmake.yml

@@ -1,16 +1,10 @@
 name: C/C++ CI
 
 on:
-  push:
-    branches: [ '**' ]
+  workflow_dispatch:
   pull_request:
     branches: [ main ]
 
-# cancel older, redundant runs of same workflow on same branch
-concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.ref_name }}
-  cancel-in-progress: true
-
 jobs:
   build:
     name: ${{ matrix.spec.name }}