fix(ci): setup libclang and reorder FFmpeg library download

- Install libclang and LLVM 18 dependencies needed for generator
- Move FFmpeg libraries download step before build verification
- Set required environment variables for CGO compilation
- Remove redundant FFmpeg download before test execution

Author: flexiondotorg

.github/workflows/go-release.yml

@@ -36,13 +36,22 @@ jobs:
           go-version: '1.24'
           cache: true
 
+      - name: Install libclang for generator
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libclang-18-dev llvm-18-dev
+          echo "CGO_LDFLAGS=-L/usr/lib/llvm-18/lib" >> $GITHUB_ENV
+          echo "CGO_CFLAGS=-I/usr/lib/llvm-18/include" >> $GITHUB_ENV
+          echo "LD_LIBRARY_PATH=/usr/lib/llvm-18/lib:$LD_LIBRARY_PATH" >> $GITHUB_ENV
+
+      - name: Download FFmpeg libraries
+        run: go run ./cmd/download-lib/
+
       - name: Verify module builds
         run: go build -v ./...
 
       - name: Run tests
-        run: |
-          go run ./cmd/download-lib/
-          go test -v ./...
+        run: go test -v ./...
 
       - name: Create tag (workflow_dispatch only)
         if: github.event_name == 'workflow_dispatch'