Update build workflow.

.github/workflows/build.yml

@@ -15,6 +15,8 @@ jobs:
     - uses: actions/checkout@v2
       with:
         submodules: recursive
+    - name: Run apt update
+      run: sudo apt update
     - name: Install LibELF
       run: sudo apt install -y libelf-dev
     - name: Install LibConfig