chore: remove download prefix and work with relative paths

make/announce.mk

@@ -10,6 +10,6 @@ $(ANNOUNCEMENT_FILE): $(ANNOUNCE) $(PYTHON_NEEDED) build/export_apkgs.py
 		--out $@ \
 		--title '$(PACK_TITLE)' \
 		--repo $(GITLAB_REPO) \
-		--releaseDir $(DOWNLOAD_PREFIX)$(RELEASE_DIR) \
+		--releaseDir $(RELEASE_DIR) \
 		$(addprefix --apkg , \
 			$(patsubst %,'%',$(APKGS)))

make/defs.mk

@@ -6,7 +6,8 @@ K := $(foreach exec,$(REQUIRED_ON_PATH), \
 # root like in CI, otherwise all generated files are in artifacts/
 # note that using . and ./ behave the same as the empty string and the filename
 # targets will not start with .
-BUILD_PREFIX ?= $(PWD)/artifacts
+BUILD_PREFIX ?= artifacts
+# make empty or add trailing slash
 BUILD_PREFIX := $(and $(filter-out . ./,$(BUILD_PREFIX)),$(BUILD_PREFIX)/)
 # some build subprocesses need this, e.g. the JS proxy for parcel needs to
 # know where to load the chardata from