Don't copy apns-conf.xml for apps-only build

http://b/issue?id=2796939
This can fix commands mm and mmm in an unbundled branch.
The cause is that mm & mmm depends on phony target "files", which includes apns-conf.xml.

Change-Id: I72ce1c7c5ddfdcd3bbea5cb9645ca3a48ff8ac12
diff --git a/core/main.mk b/core/main.mk
index ae7abb6..32d67e9 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -282,6 +282,7 @@
   ADDITIONAL_BUILD_PROPERTIES += dalvik.vm.dexopt-flags=m=y
 endif
 
+ifeq (,$(TARGET_BUILD_APPS))
 # Install an apns-conf.xml file if one's not already being installed.
 ifeq (,$(filter %:system/etc/apns-conf.xml, $(PRODUCT_COPY_FILES)))
   PRODUCT_COPY_FILES += \
@@ -302,6 +303,7 @@
     endif
   endif
 endif
+endif # !TARGET_BUILD_APPS
 
 ADDITIONAL_BUILD_PROPERTIES += net.bt.name=Android