Avoid duplicate workflow runs

.github/workflows/build.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   dists-and-docs:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3

.github/workflows/lint.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   check:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3

.github/workflows/test.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   pytest:
     runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3