Prevent double ci run if both push and pr happen

.github/workflows/linux.yml

@@ -11,6 +11,7 @@ jobs:
   # -----------------------------------------------------------------------
   build:
     runs-on: ubuntu-latest
+    if: github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.action == 'opened')
     defaults:
       run:
         shell: bash

.github/workflows/macos.yml

@@ -8,6 +8,7 @@ permissions:
 jobs:
   build:
     runs-on: macOS-latest
+    if: github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.action == 'opened')
     name: "macOS Clang (C++11, Release)"
     steps:
       - uses: actions/checkout@v4

.github/workflows/windows.yml

@@ -8,6 +8,7 @@ permissions:
 jobs:
   build:
     runs-on: windows-latest
+    if: github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.action == 'opened')
     strategy:
       fail-fast: true
       matrix: