package: ignore failed downloads with IGNORE_ERRORS

When IGNORE_ERROR is set, also skip broken downloads, this is required
to make a full "make download" run even if some upstream sources are
unreachable.

package/Makefile

@@ -17,6 +17,7 @@ else
   $(curdir)/builddirs-install:=. $(filter-out base-files,$(sort $(package-y))) $(filter base-files,$(package-y))
 endif
 ifneq ($(IGNORE_ERRORS),)
+  $(curdir)/builddirs-ignore-download := $(foreach m,$(package-ignore-errors),$(package-$(m)-filter))
   $(curdir)/builddirs-ignore-compile:= $(if $(filter n m y, $(IGNORE_ERRORS)),$(foreach m,$(IGNORE_ERRORS),$(package-$(subst n,,$(m)))),$(package-m) $(package-))
 endif