Run CI tests single threaded to avoid output mangling

This way, the error should always be at/near the bottom, so it's easier to find.

Author: phil-opp

.github/workflows/ci.yml

@@ -65,7 +65,7 @@ jobs:
       - name: Run api tests
         run: cargo test -p bootloader_api
       - name: Run integration tests
-        run: cargo test
+        run: cargo test -- --test-threads 1
 
       # test feature gates (only on one OS is enough)
       - name: Test with only UEFI feature