package/pkg-generic.mk: make HOST_<pkg>_DL_OPTS inherit from <pkg>_DL_OPTS

Just like _SITE, _SOURCE, _SITE_METHOD, it is very likely that if
<pkg>_DL_OPTS is defined, the same value should be used for
HOST_<pkg>_DL_OPTS, so let's have the same inheritance logic than the
one we have for other variables.

Fixes:

  https://bugs.busybox.net/show_bug.cgi?id=12321

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 085f32c17b408fbac68d92232b42d49e883e1f69)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-generic.mk

@@ -538,6 +538,12 @@ ifndef $(2)_SITE_METHOD
  endif
 endif
 
+ifndef $(2)_DL_OPTS
+ ifdef $(3)_DL_OPTS
+  $(2)_DL_OPTS = $$($(3)_DL_OPTS)
+ endif
+endif
+
 ifneq ($$(filter bzr cvs hg svn,$$($(2)_SITE_METHOD)),)
 BR_NO_CHECK_HASH_FOR += $$($(2)_SOURCE)
 endif