Fix GitHub Actions workflow.

.github/workflows/main.yml

@@ -12,7 +12,6 @@ permissions:
 
 defaults:
   run:
-    # necessary for windows
     shell: bash
 
 jobs:
@@ -81,6 +80,7 @@ jobs:
           # dependencies are only needed on ubuntu as that's the only place where
           # we make cross-compilation
           if [[ $OS =~ ^ubuntu.*$ ]]; then
+            sudo apt-get update -qq
             sudo apt-get install -qq crossbuild-essential-arm64 crossbuild-essential-armhf musl-tools
           fi
           # some additional configuration for cross-compilation on linux