Don't enable LOCAL_DEX_PREOPT for apks outside system.img

Bug: 15621103
Change-Id: If267a4aaad17b66d9779169237e06d65d67f088f
diff --git a/core/dex_preopt_odex_install.mk b/core/dex_preopt_odex_install.mk
index caaa16d..613b058 100644
--- a/core/dex_preopt_odex_install.mk
+++ b/core/dex_preopt_odex_install.mk
@@ -9,11 +9,13 @@
 else # WITH_DEXPREOPT=true
   ifeq (,$(TARGET_BUILD_APPS)) # TARGET_BUILD_APPS empty
     ifndef LOCAL_DEX_PREOPT # LOCAL_DEX_PREOPT undefined
-      ifeq (,$(LOCAL_APK_LIBRARIES)) # LOCAL_APK_LIBRARIES empty
-        LOCAL_DEX_PREOPT := $(DEX_PREOPT_DEFAULT)
-      else # LOCAL_APK_LIBRARIES not empty
-        LOCAL_DEX_PREOPT := nostripping
-      endif # LOCAL_APK_LIBRARIES not empty
+      ifneq ($(filter $(TARGET_OUT)/%,$(my_module_path)),) # Installed to system.img.
+        ifeq (,$(LOCAL_APK_LIBRARIES)) # LOCAL_APK_LIBRARIES empty
+          LOCAL_DEX_PREOPT := $(DEX_PREOPT_DEFAULT)
+        else # LOCAL_APK_LIBRARIES not empty
+          LOCAL_DEX_PREOPT := nostripping
+        endif # LOCAL_APK_LIBRARIES not empty
+      endif # Installed to system.img.
     endif # LOCAL_DEX_PREOPT undefined
   endif # TARGET_BUILD_APPS empty
 endif # WITH_DEXPREOPT=true