build/init: allow to have an empty GRUB_CMDLINE_LINUX_DEFAULT
build/init: allow to have an empty GRUB_CMDLINE_LINUX_DEFAULT

enovance/edeploy,redhat-cip/edeploy,lebauce/edeploy,enovance/edeploy,redhat-cip/edeploy,enovance/edeploy,redhat-cip/edeploy,lebauce/edeploy,lebauce/edeploy,lebauce/edeploy,redhat-cip/edeploy,enovance/edeploy