Turn shared library multilib warnings into errors

When caught later, these just get turned into warnings with
unpredictable results, or non-obvious errors.

Change-Id: Ie7ba88e97dc5bedd6cf850748d79693711ac41da
diff --git a/core/shared_library.mk b/core/shared_library.mk
index 71a3bb2..73aca78c 100644
--- a/core/shared_library.mk
+++ b/core/shared_library.mk
@@ -9,13 +9,13 @@
 ifeq ($(my_module_multilib),both)
 ifneq ($(LOCAL_MODULE_PATH),)
 ifneq ($(TARGET_2ND_ARCH),)
-$(warning $(LOCAL_MODULE): LOCAL_MODULE_PATH for shared libraries is unsupported in multiarch builds, use LOCAL_MODULE_RELATIVE_PATH instead)
+$(error $(LOCAL_MODULE): LOCAL_MODULE_PATH for shared libraries is unsupported in multiarch builds, use LOCAL_MODULE_RELATIVE_PATH instead)
 endif
 endif
 
 ifneq ($(LOCAL_UNSTRIPPED_PATH),)
 ifneq ($(TARGET_2ND_ARCH),)
-$(warning $(LOCAL_MODULE): LOCAL_UNSTRIPPED_PATH for shared libraries is unsupported in multiarch builds)
+$(error $(LOCAL_MODULE): LOCAL_UNSTRIPPED_PATH for shared libraries is unsupported in multiarch builds)
 endif
 endif
 endif # my_module_multilib == both