ci: switch from Cirrus to Github Actions

test/ci/build.sh

@@ -3,19 +3,17 @@
 # This script can also be run locally for testing:
 #   ./build.sh <scenario>
 #
-# When variable CIRRUS_CI is unset, this script leaves no persistent traces on the host system.
+# When variable GITHUB_ACTIONS is unset, this script leaves no persistent traces on the host system.
 
 set -euo pipefail
 
 scenario=$1
 
-if [[ -v CIRRUS_CI ]]; then
+if [[ -v GITHUB_ACTIONS ]]; then
     if [[ ! -e /dev/kvm ]]; then
         >&2 echo "No KVM available on VM host."
         exit 1
     fi
-    # Enable KVM access for nixbld users
-    chmod o+rw /dev/kvm
 fi
 
 cd "${BASH_SOURCE[0]%/*}"