build: add zstd support to pack/unpack functions

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

include/download.mk

@@ -50,6 +50,7 @@ endef
 dl_pack/bz2=bzip2 -c > $(1)
 dl_pack/gz=gzip -nc > $(1)
 dl_pack/xz=xz -zc -7e > $(1)
+dl_pack/zst=zstd -T0 --ultra -20 -c > $(1)
 dl_pack/unknown=$(error ERROR: Unknown pack format for file $(1))
 define dl_pack
 	$(if $(dl_pack/$(call ext,$(1))),$(dl_pack/$(call ext,$(1))),$(dl_pack/unknown))

include/unpack.mk

@@ -31,6 +31,10 @@ ifeq ($(strip $(UNPACK_CMD)),)
       EXT:=$(call ext,$(PKG_SOURCE:.$(EXT)=))
       DECOMPRESS_CMD:=xzcat $(DL_DIR)/$(PKG_SOURCE) |
     endif
+    ifeq (zst,$(EXT))
+      EXT:=$(call ext,$(PKG_SOURCE:.$(EXT)=))
+      DECOMPRESS_CMD:=zstdcat $(DL_DIR)/$(PKG_SOURCE) |
+    endif
     ifeq ($(filter tgz tbz tbz2 txz,$(EXT1)),$(EXT1))
       EXT:=tar
     endif