fix github ci?

Author: kloenk

.github/workflows/ci.yaml

@@ -13,6 +13,7 @@ jobs:
     steps:
       # Setup
       - uses: actions/checkout@v2
+      - run: sudo apt update
       - run: sudo apt install libelf-dev qemu-system-x86 busybox-static
       - run: rustup default nightly-2020-08-27
       - run: rustup component add rust-src