Allow arm prebuilts for x86_arm builds

But only for static and shared libraries -- we disable building other
types of modules for arm, so don't support the prebuilts for them
either.

This is needed so that we can build these libraries under Soong, and
expose them to Make using BUILD_PREBUILT.

Bug: 27526885
Change-Id: I4f6ec922aed37591b6257b7022b81fb65d05b0fe

core/prebuilt.mk

@@ -13,7 +13,10 @@ else
   my_prefix := TARGET_
 
   ifeq ($(TARGET_TRANSLATE_2ND_ARCH),true)
-    LOCAL_MULTILIB := first
+    # Only support prebuilt shared and static libraries for translated arch
+    ifeq ($(filter SHARED_LIBRARIES STATIC_LIBRARIES,$(LOCAL_MODULE_CLASS)),)
+      LOCAL_MULTILIB := first
+    endif
   endif
 endif