build: use correct arm vs thumb arguments for 2nd arch builds

Set arm_objects_mode and normal_objects_mode when building a
module for arm when it is the 2nd arch.

Change-Id: I5f7df519b6e1dde6cbf92d106681f07a58e1f1f2
diff --git a/core/binary.mk b/core/binary.mk
index a3a9c16..3582ba0 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -281,7 +281,7 @@
 ## Define arm-vs-thumb-mode flags.
 ###########################################################
 LOCAL_ARM_MODE := $(strip $(LOCAL_ARM_MODE))
-ifeq ($(TARGET_ARCH),arm)
+ifeq ($(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH),arm)
 arm_objects_mode := $(if $(LOCAL_ARM_MODE),$(LOCAL_ARM_MODE),arm)
 normal_objects_mode := $(if $(LOCAL_ARM_MODE),$(LOCAL_ARM_MODE),thumb)