pkgpriorities: also needed for rootfs

This should have better been done through some shared code
but it's not that obvious...

features.in/pkgpriorities/rootfs/lib/50-pkgpriorities.mk

@@ -0,0 +1,26 @@
+_IMAGE_APTBOX_ = $(WORKDIR)/chroot/$(WORKDIRNAME)/aptbox
+
+# Add prerequisite to the build-image target of
+# $(MKIMAGE_PREFIX)/targets.mk.
+build-image: $(_IMAGE_APTBOX_)/etc/apt/pkgpriorities
+
+_PINNED_PACKAGES_ = $(foreach pp,$(PINNED_PACKAGES),$(if $(findstring :,$(pp)),$(pp),$(pp):$(PIN_PRIORITY)))
+_PIN_PRIORITIES_ = $(sort $(foreach pp,$(_PINNED_PACKAGES_),$(lastword $(subst :, ,$(pp)))))
+_PKGPRIORITIES_ = $(subst \n ,\n,$(foreach pri,$(_PIN_PRIORITIES_),$(pri):$(patsubst %:$(pri),\n   %,$(filter %:$(pri),$(_PINNED_PACKAGES_)))\n))
+
+$(_IMAGE_APTBOX_)/etc/apt/pkgpriorities: prepare-image-workdir
+	@echo -e '$(_PKGPRIORITIES_)' | sed -e 's,[[:space:]]\+$$,,' >$@
+	@if [ -s $@ ]; then \
+		if grep -q '^\(APT::\)\?Dir::Etc::pkgpriorities[[:space:]]' \
+			$(_IMAGE_APTBOX_)/etc/apt/apt.conf; \
+		then \
+			sed -i -e 's,\(Dir::Etc::pkgpriorities\)[[:space:]].*$$,\1 "$@";,g' \
+				$(_IMAGE_APTBOX_)/etc/apt/apt.conf; \
+		else \
+			echo 'Dir::Etc::pkgpriorities "$@";' \
+				>>$(_IMAGE_APTBOX_)/etc/apt/apt.conf; \
+		fi; \
+		echo "--- Package priorities ---" >&2; \
+		cat $@ >&2; \
+		echo "---" >&2; \
+	fi