package/pkg-download: export TAR for download backends

Later commits will start using this variable.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
[Arnout: quote TAR="..."]
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
(cherry picked from commit ce6b48c2cf2811b769b03bb2d010d93537b2c176)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-download.mk

@@ -107,7 +107,9 @@ endif
 
 define DOWNLOAD
 	$(Q)mkdir -p $($(2)_DL_DIR)
-	$(Q)$(EXTRA_ENV) $($(2)_DL_ENV) \
+	$(Q)$(EXTRA_ENV) \
+	$($(2)_DL_ENV) \
+	TAR="$(TAR)" \
 	BR_NO_CHECK_HASH_FOR="$(if $(BR2_DOWNLOAD_FORCE_CHECK_HASHES),,$(BR_NO_CHECK_HASH_FOR))" \
 		flock $($(2)_DL_DIR)/.lock $(DL_WRAPPER) \
 		-c '$($(2)_DL_VERSION)' \