Install config files after buildroot compile

Saves build time when only making minor config changes.

Signed-off-by: Kyle Harding <kyle@balena.io>

Dockerfile

@@ -1,5 +1,6 @@
 #syntax=docker/dockerfile:1.2
 
+# set by buildkit (DOCKER_BUILDKIT=1)
 # hadolint ignore=DL3029
 FROM --platform=$BUILDPLATFORM debian:bullseye-20211220-slim AS buildroot-base
 
@@ -42,8 +43,11 @@ FROM buildroot-base as rootfs
 
 WORKDIR /home/br-user/buildroot
 
+# set by buildkit (DOCKER_BUILDKIT=1)
 ARG TARGETARCH
 ARG TARGETVARIANT
+
+# musl or glibc (musl is smaller)
 ARG ROOTFS_LIBC=musl
 
 COPY *.patch ./
@@ -53,12 +57,9 @@ RUN git apply ./*.patch
 COPY config ./config
 
 RUN support/kconfig/merge_config.sh -m \
-	config/common.cfg \
 	config/arch/"${TARGETARCH}${TARGETVARIANT}".cfg \
 	config/libc/"${ROOTFS_LIBC}".cfg \
-	config/unbound.cfg
-
-COPY rootfs_overlay ./rootfs_overlay
+	config/*.cfg
 
 RUN --mount=type=cache,target=/cache,uid=1000,gid=1000,sharing=private \
     make olddefconfig && make source && make
@@ -74,4 +75,6 @@ FROM scratch
 
 COPY --from=rootfs rootfs/ /
 
+COPY --chown=unbound:unbound rootfs_overlay/ /
+
 ENTRYPOINT [ "unbound" ]

config/device_table.txt

@@ -1,2 +0,0 @@
-/etc/unbound d 750 unbound unbound - - - - -
-/etc/unbound/root.key f 750 unbound unbound - - - - -

config/unbound.cfg

@@ -3,6 +3,4 @@ BR2_PACKAGE_BIND_SERVER=n
 BR2_PACKAGE_BIND_TOOLS=y
 BR2_PACKAGE_UNBOUND=y
 BR2_PACKAGE_UNBOUND_DNSCRYPT=y
-BR2_ROOTFS_OVERLAY="$(TOPDIR)/rootfs_overlay"
 BR2_ROOTFS_USERS_TABLES="$(TOPDIR)/config/users_table.txt"
-BR2_ROOTFS_DEVICE_TABLE="$(TOPDIR)/config/device_table.txt"