[skip changelog] Disable scheduled workflows that would always fail from running in forks (#888)

* Disable workflows that would always fail from running in forks

These workflows use resources that are only available when run in the arduino/arduino-cli repository, so would always fail when they run in a repository. They are of no value to fork repositories. They are triggered by the schedule event, so they cause regular annoying and confusing workflow failure notifications for every fork owner.

* Don't trigger link validation CI workflow on schedule event when in a fork

.github/workflows/arduino-stats.yaml

@@ -7,6 +7,9 @@ on:
 
 jobs:
   push-stats:
+    # This workflow is only of value to the arduino/arduino-cli repository and
+    # would always fail in forks
+    if: github.repository == 'arduino/arduino-cli'
     runs-on: ubuntu-latest
 
     steps:

.github/workflows/github-stats.yaml

@@ -7,6 +7,9 @@ on:
 
 jobs:
   push-stats:
+    # This workflow is only of value to the arduino/arduino-cli repository and
+    # would always fail in forks
+    if: github.repository == 'arduino/arduino-cli'
     runs-on: ubuntu-latest
 
     steps:

.github/workflows/i18n-nightly-push.yaml

@@ -7,6 +7,9 @@ on:
 
 jobs:
   push-to-transifex:
+    # This workflow is only of value to the arduino/arduino-cli repository and
+    # would always fail in forks
+    if: github.repository == 'arduino/arduino-cli'
     runs-on: ubuntu-latest
     steps:
       - name: Checkout

.github/workflows/i18n-weekly-pull.yaml

@@ -7,6 +7,9 @@ on:
 
 jobs:
   pull-from-transifex:
+    # This workflow is only of value to the arduino/arduino-cli repository and
+    # would always fail in forks
+    if: github.repository == 'arduino/arduino-cli'
     runs-on: ubuntu-latest
     steps:
       - name: Checkout

.github/workflows/link-validation.yaml

@@ -8,6 +8,8 @@ on:
 
 jobs:
   verify-links:
+    # Don't trigger on schedule event when in a fork
+    if: github.event_name != 'schedule' || (github.event_name == 'schedule' && github.repository == 'arduino/arduino-cli')
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2

.github/workflows/nightly.yaml

@@ -7,6 +7,9 @@ on:
 
 jobs:
   create-nightly-artifacts:
+    # This workflow is only of value to the arduino/arduino-cli repository and
+    # would always fail in forks
+    if: github.repository == 'arduino/arduino-cli'
     runs-on: ubuntu-latest
 
     container: