Add retry mechanism for updating dependencies

Implement retry logic for 'lake update' step in CI workflow.

Author: SmaniaD

.github/workflows/build.yml

@@ -9,23 +9,19 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      # 1. Clona o repositório
       - uses: actions/checkout@v3
 
-      # 2. Cache do elan (Lean toolchain)
       - name: Cache elan
         uses: actions/cache@v3
         with:
           path: ~/.elan
           key: ${{ runner.os }}-elan-${{ hashFiles('lean-toolchain') }}
 
-      # 3. Instala Lean (rápido se vier do cache)
       - name: Install Lean
         run: |
           curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh -s -- -y
           echo "$HOME/.elan/bin" >> $GITHUB_PATH
 
-      # 4. Cache do projeto (.lake + deps)
       - name: Cache lake
         uses: actions/cache@v3
         with:
@@ -34,11 +30,16 @@ jobs:
             build
           key: ${{ runner.os }}-lake-${{ hashFiles('lakefile.lean') }}
 
-      # 5. Baixa dependências
       - name: Update deps
-        run: lake update
+        run: |
+          for i in 1 2 3; do
+            lake update && exit 0
+            echo "lake update failed, retry $i/3"
+            sleep 10
+          done
+          exit 1
 
-      # 6. Build
       - name: Build
-        run: lake build 
+        run: lake build
+