feat: add caching to workflow

.github/workflows/validate.yml

@@ -10,11 +10,31 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - run: sudo apt-get install -y yara
-      - run: |
+
+      - name: Cache YARA
+        uses: actions/cache@v2
+        id: cache-yara
+        with:
+          path: "/usr/local/bin/yara"
+          key: ${{ secrets.YARA_VERSION }}
+
+      - name: Install YARA
+        env:
+          CACHE_HIT: ${{ steps.cache-yara.outputs.cache-hit }}
+          YARA_VERSION: ${{ secrets.YARA_VERSION }}
+        run: |
+          if [[ "$CACHE_HIT" == 'true' ]]; then
+            echo "cache found, skipping install"
+          else
+            sudo apt-get install -y yara
+            mkdir -p ~/yara
+            sudo cp /usr/local/bin/yara ~/yara/
+          fi
+
+      - name: Validate YARA
+        run: |
           output=$(find . -type f -iname "*.yara" -exec yara -w {} /dev/null \; 2>&1)
-          echo "$output"
           if echo "$output" | grep -q 'syntax error'; then
-            echo "syntax error"
+            echo "$output"
             exit 1
           fi