chore: fix dockerfile warnings

This fixes the rather irksome warning when using buildkit to build
images.

This should not break anything since the defaults are set to `scratch`
and if the `build-arg` is not passed the copy stage will fail.

Signed-off-by: Noel Georgi <[email protected]>

Dockerfile

@@ -2,49 +2,49 @@
 
 # Meta args applied to stage base names.
 
-ARG TOOLS
-ARG PKGS
-ARG EXTRAS
-ARG INSTALLER_ARCH
-ARG DEBUG_TOOLS_SOURCE
-
-ARG PKGS_PREFIX
-ARG PKG_FHS
-ARG PKG_CA_CERTIFICATES
-ARG PKG_CRYPTSETUP
-ARG PKG_CONTAINERD
-ARG PKG_DOSFSTOOLS
-ARG PKG_E2FSPROGS
-ARG PKG_SYSTEMD_UDEVD
-ARG PKG_LIBCAP
-ARG PKG_GRUB
-ARG PKG_SD_BOOT
-ARG PKG_IPTABLES
-ARG PKG_IPXE
-ARG PKG_LIBINIH
-ARG PKG_LIBJSON_C
-ARG PKG_LIBPOPT
-ARG PKG_LIBSEPOL
-ARG PKG_LIBSELINUX
-ARG PKG_PCRE2
-ARG PKG_LIBURCU
-ARG PKG_OPENSSL
-ARG PKG_LIBSECCOMP
-ARG PKG_LINUX_FIRMWARE
-ARG PKG_LVM2
-ARG PKG_LIBAIO
-ARG PKG_MUSL
-ARG PKG_RUNC
-ARG PKG_XFSPROGS
-ARG PKG_APPARMOR
-ARG PKG_UTIL_LINUX
-ARG PKG_KMOD
-ARG PKG_KERNEL
-ARG PKG_CNI
-ARG PKG_FLANNEL_CNI
-ARG PKG_TALOSCTL_CNI_BUNDLE_INSTALL
-
-ARG DEBUG_TOOLS_SOURCE
+ARG TOOLS=scratch
+ARG PKGS=scratch
+ARG EXTRAS=scratch
+ARG INSTALLER_ARCH=scratch
+ARG DEBUG_TOOLS_SOURCE=scratch
+
+ARG PKGS_PREFIX=scratch
+ARG PKG_FHS=scratch
+ARG PKG_CA_CERTIFICATES=scratch
+ARG PKG_CRYPTSETUP=scratch
+ARG PKG_CONTAINERD=scratch
+ARG PKG_DOSFSTOOLS=scratch
+ARG PKG_E2FSPROGS=scratch
+ARG PKG_SYSTEMD_UDEVD=scratch
+ARG PKG_LIBCAP=scratch
+ARG PKG_GRUB=scratch
+ARG PKG_SD_BOOT=scratch
+ARG PKG_IPTABLES=scratch
+ARG PKG_IPXE=scratch
+ARG PKG_LIBINIH=scratch
+ARG PKG_LIBJSON_C=scratch
+ARG PKG_LIBPOPT=scratch
+ARG PKG_LIBSEPOL=scratch
+ARG PKG_LIBSELINUX=scratch
+ARG PKG_PCRE2=scratch
+ARG PKG_LIBURCU=scratch
+ARG PKG_OPENSSL=scratch
+ARG PKG_LIBSECCOMP=scratch
+ARG PKG_LINUX_FIRMWARE=scratch
+ARG PKG_LVM2=scratch
+ARG PKG_LIBAIO=scratch
+ARG PKG_MUSL=scratch
+ARG PKG_RUNC=scratch
+ARG PKG_XFSPROGS=scratch
+ARG PKG_APPARMOR=scratch
+ARG PKG_UTIL_LINUX=scratch
+ARG PKG_KMOD=scratch
+ARG PKG_KERNEL=scratch
+ARG PKG_CNI=scratch
+ARG PKG_FLANNEL_CNI=scratch
+ARG PKG_TALOSCTL_CNI_BUNDLE_INSTALL=scratch
+
+ARG DEBUG_TOOLS_SOURCE=scratch
 
 # Resolve package images using ${PKGS} to be used later in COPY --from=.