chore(ci): allow external contribution in fast aws tests workflow

.github/workflows/aws_tfhe_fast_tests.yml

@@ -11,12 +11,13 @@ env:
   SLACK_ICON: https://pbs.twimg.com/profile_images/1274014582265298945/OjBKP9kn_400x400.png
   SLACK_USERNAME: ${{ secrets.BOT_USERNAME }}
   SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}
-  IS_PULL_REQUEST: ${{ github.event_name == 'pull_request' }}
+  IS_PULL_REQUEST: ${{ github.event_name == 'pull_request' || github.event_name == 'pull_request_target' }}
 
 on:
   # Allows you to run this workflow manually from the Actions tab as an alternative.
   workflow_dispatch:
   pull_request:
+  pull_request_target:
 
 jobs:
   should-run:
@@ -55,6 +56,7 @@ jobs:
         with:
           fetch-depth: 0
           token: ${{ secrets.FHE_ACTIONS_TOKEN }}
+          ref: ${{ github.event.pull_request.head.sha }}
 
       - name: Check for file changes
         id: changed-files
@@ -157,6 +159,7 @@ jobs:
         with:
           persist-credentials: 'false'
           token: ${{ secrets.FHE_ACTIONS_TOKEN }}
+          ref: ${{ github.event.pull_request.head.sha }}
 
       - name: Install latest stable
         uses: dtolnay/rust-toolchain@a54c7afa936fefeb4456b2dd8068152669aa8203