build: add support for LOCAL_MULTILIB := 64

I don't expect it to be useful for modules, but package.mk will
use it to only install 64-bit native apps on devices that
only have a 64-bit zygote.

Change-Id: If3f5a81c3a60bd13fa6ded08e2a7579a29877324
diff --git a/core/multilib.mk b/core/multilib.mk
index fa5397a..8380249 100644
--- a/core/multilib.mk
+++ b/core/multilib.mk
@@ -20,7 +20,7 @@
 my_module_multilib := first
 endif
 else # my_module_multilib defined
-ifeq (,$(filter 32 first both none,$(my_module_multilib)))
+ifeq (,$(filter 32 64 first both none,$(my_module_multilib)))
 $(error $(LOCAL_PATH): Invalid LOCAL_MULTILIB specified for module $(LOCAL_MODULE))
 endif
 endif # my_module_multilib defined