github: limit resource usage

We had a hanging build of the nixos tests. It might be we hit some IO or
memory limit because of too much parallism. Try to limit resource usage
a bit.

Signed-off-by: Stefan Kober <stefan.kober@cyberus-technology.de>
On-behalf-of: SAP stefan.kober@sap.com

Author: hertrste

.github/workflows/qa.yml

@@ -20,7 +20,7 @@ jobs:
           extra_nix_config: "system-features = nixos-test benchmark big-parallel kvm"
       - name: Build
         run: |
-          nix build -Lv .#tests.x86_64-linux.openstack-default-setup.driver
+          nix build -Lv --options max-jobs 2 --option cores 4 .#tests.x86_64-linux.openstack-default-setup.driver
       - name: Basic setup
         run: |
           nix run .#tests.x86_64-linux.openstack-default-setup.driver