package/pkg-utils: teach per-package-rsync to copy or hardlink dest

commit 21d52e52d8de (package/pkg-utils.mk: break hardlinks in global
{TARGET, HOST}_DIR on per-package build) was recently reverted, so we
are back to a situation where it is possible for packages and post-build
scripts to modify files in-place, and thus impact files in any arbitrary
per-package directory, which may break things on rebuild for example.

21d52e52d8de was too big a hammer, but we can still apply the reasoning
from it, to the aggregation of the final target and host directories.

This solves the case for post-build scripts at least. We leave the case
of inter-package modification aside, as it is a bigger issue that will
need more than just copying files around.

We use --hard-links, so that hard-links in the source (the PPD), are
kept as new hard-links (i.e. "copy" of hard-links) in the destination.
This contributes to limiting the size of target/.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Herve Codina <herve.codina@bootlin.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: Herve Codina <herve.codina@bootlin.com>

Makefile

@@ -717,7 +717,7 @@ STAGING_DIR_FILES_LISTS = $(sort $(wildcard $(BUILD_DIR)/*/.files-list-staging.t
 .PHONY: host-finalize
 host-finalize: $(PACKAGES) $(HOST_DIR) $(HOST_DIR_SYMLINK)
 	@$(call MESSAGE,"Finalizing host directory")
-	$(call per-package-rsync,$(sort $(PACKAGES)),host,$(HOST_DIR))
+	$(call per-package-rsync,$(sort $(PACKAGES)),host,$(HOST_DIR),copy)
 
 .PHONY: staging-finalize
 staging-finalize: $(STAGING_DIR_SYMLINK)
@@ -725,7 +725,7 @@ staging-finalize: $(STAGING_DIR_SYMLINK)
 .PHONY: target-finalize
 target-finalize: $(PACKAGES) $(TARGET_DIR) host-finalize
 	@$(call MESSAGE,"Finalizing target directory")
-	$(call per-package-rsync,$(sort $(PACKAGES)),target,$(TARGET_DIR))
+	$(call per-package-rsync,$(sort $(PACKAGES)),target,$(TARGET_DIR),copy)
 	$(foreach hook,$(TARGET_FINALIZE_HOOKS),$($(hook))$(sep))
 	rm -rf $(TARGET_DIR)/usr/include $(TARGET_DIR)/usr/share/aclocal \
 		$(TARGET_DIR)/usr/lib/pkgconfig $(TARGET_DIR)/usr/share/pkgconfig \

package/pkg-utils.mk

@@ -214,10 +214,19 @@ ifeq ($(BR2_PER_PACKAGE_DIRECTORIES),y)
 # $1: space-separated list of packages to rsync from
 # $2: 'host' or 'target'
 # $3: destination directory
+# $4: literal "copy" or "hardlink" to copy or hardlink files from src to dest
 define per-package-rsync
 	mkdir -p $(3)
 	$(foreach pkg,$(1),\
-		rsync -a --link-dest=$(PER_PACKAGE_DIR)/$(pkg)/$(2)/ \
+		rsync -a \
+			--hard-links \
+			$(if $(filter hardlink,$(4)), \
+				--link-dest=$(PER_PACKAGE_DIR)/$(pkg)/$(2)/, \
+				$(if $(filter copy,$(4)), \
+					$(empty), \
+					$(error per-package-rsync can only "copy" or "hardlink", not "$(4)") \
+				) \
+			) \
 			$(PER_PACKAGE_DIR)/$(pkg)/$(2)/ \
 			$(3)$(sep))
 endef
@@ -230,8 +239,8 @@ endef
 #
 # $1: space-separated list of packages to rsync from
 define prepare-per-package-directory
-	$(call per-package-rsync,$(1),host,$(HOST_DIR))
-	$(call per-package-rsync,$(1),target,$(TARGET_DIR))
+	$(call per-package-rsync,$(1),host,$(HOST_DIR),hardlink)
+	$(call per-package-rsync,$(1),target,$(TARGET_DIR),hardlink)
 endef
 
 # Ensure files like .la, .pc, .pri, .cmake, and so on, point to the