Default to buildkit (#331)

* use buildkit to skip adding context

* also build system with buildkit

build_kernel.sh

@@ -24,6 +24,7 @@ fi
 
 # Setup kernel build container
 echo "Building agnos-meta-builder docker image"
+export DOCKER_BUILDKIT=1
 docker build -f Dockerfile.builder -t agnos-meta-builder $DIR \
   --build-arg UNAME=$(id -nu) \
   --build-arg UID=$(id -u) \

build_system.sh

@@ -46,6 +46,7 @@ if [ "$ARCH" = "x86_64" ]; then
 fi
 
 # Check agnos-builder Dockerfile
+export DOCKER_BUILDKIT=1
 docker build -f Dockerfile.agnos --check $DIR
 
 # Start agnos-builder docker build and create container