Merge pull request RIOT-OS#20689 from bmewen/cachedir-tag

Makefile.include: creation of CACHEDIR.TAG as a dependency of pkg-prepare

Makefile.include

@@ -688,7 +688,6 @@ BUILDDEPS += $(RIOTBUILD_CONFIG_HEADER_C)
 BUILDDEPS += pkg-prepare
 BUILDDEPS += $(APPDEPS)
 BUILDDEPS += $(MODULE_LIST_DIR)
-BUILDDEPS += $(BUILD_DIR)/CACHEDIR.TAG
 
 # Build dependencies depend on clean (if a make goal), as clean may wipe them.
 # Without them depending on clean parallel builds occasionally fail due to
@@ -756,11 +755,6 @@ $(_SUBMAKE_LIBS): $(APPLICATION_MODULE).module pkg-build $(GENSRC)
 print-size: $(ELFFILE)
 	$(Q)$(SIZE) $(SIZEFLAGS) $<
 
-$(BUILD_DIR)/CACHEDIR.TAG:
-	$(Q)mkdir -p "$(BUILD_DIR)"
-	$(Q)echo "Signature: 8a477f597d28d172789f06886806bc55" > "$@"
-	$(Q)echo "# This folder contains RIOT's build cache" >> "$@"
-
 %.hex: %.elf
 	$(Q)$(OBJCOPY) $(OFLAGS) -Oihex $< $@
 

pkg/pkg.mk

@@ -82,8 +82,15 @@ PKG_CUSTOM_PREPARED ?=
 # Declare 'all' first to have it being the default target
 all: prepare
 
+BUILD_DIR ?= $(RIOTBASE)/build
+
+$(BUILD_DIR)/CACHEDIR.TAG:
+	$(Q)mkdir -p "$(BUILD_DIR)"
+	$(Q)echo "Signature: 8a477f597d28d172789f06886806bc55" > "$@"
+	$(Q)echo "# This folder contains RIOT's build cache" >> "$@"
+
 # Add noop builtin to avoid "Nothing to be done for prepare" message
-prepare: $(PKG_PREPARED)
+prepare: $(PKG_PREPARED) | $(BUILD_DIR)/CACHEDIR.TAG
 	@:
 
 # Allow packages to add a custom step to be `prepared`.