kernel.bbclass: pass LD also in savedefconfig

* similar to:
  https://git.openembedded.org/openembedded-core/commit/?id=66c1f4b0abd3483759f9e4141a80f982eaf8ccfd
  https://git.openembedded.org/openembedded-core/commit/?id=36fe2efc91fec5a52374a2dc4814a69076a2d28e
  but for savedefconfig task
* otherwise with ld-is-gold it will fail with:
  gold linker is not supported as it is not capable of linking the kernel proper.

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/kernel.bbclass

@@ -629,7 +629,7 @@ kernel_do_configure() {
 
 do_savedefconfig() {
 	bbplain "Saving defconfig to:\n${B}/defconfig"
-	oe_runmake -C ${B} savedefconfig
+	oe_runmake -C ${B} LD='${KERNEL_LD}' savedefconfig
 }
 do_savedefconfig[nostamp] = "1"
 addtask savedefconfig after do_configure