Launch 'make compare' only for pret repo and not fork (#858)

Fixes #856

.github/workflows/main.yml

@@ -29,6 +29,7 @@ jobs:
           rm -rf rgbds
 
       - name: Compare
+        if: ${{ github.repository_owner == 'pret' }}
         run: |
           make DEBUG=1 -j$(nproc) compare
           if ! git diff-index --quiet HEAD --; then
@@ -37,6 +38,16 @@ jobs:
             return 1
           fi
 
+      - name: Make
+        if: ${{ github.repository_owner != 'pret' }}
+        run: |
+          make -j$(nproc)
+          if ! git diff-index --quiet HEAD --; then
+            echo 'Uncommitted changes detected:'
+            git diff-index HEAD --
+            return 1
+          fi
+
       - name: Discord webhook
         if: ${{ github.event_name == 'push' && github.repository_owner == 'pret' }}
         env: