ci: build-yocto: use the kas mirror for the ci builds

Explicitly use the kas mirror as it is no longer used by default

Signed-off-by: Jose Quaresma <[email protected]>

.github/workflows/build-yocto.yml

@@ -69,4 +69,4 @@ jobs:
           mkdir -p $SSTATE_DIR
           mkdir build
           cd build
-          kas build ../ci/${{ matrix.machine }}.yml
+          kas build ../ci/${{ matrix.machine }}.yml ../ci/mirror.yml