Fix build error

Fix the build error when TARGET_BUILD_APPS is set

Bug: None
Test: make -j40 && make -j110 showcommands dist
TARGET_BUILD_APPS='TimeZoneData TimeZoneData_test1 TimeZoneData_test2'
TARGET_BUILD_VARIANT=userdebug

Change-Id: I981b0a245d7e8f2dabbd4e51db52d17aeacc6106
diff --git a/core/apidiff.mk b/core/apidiff.mk
index 42a1d34..6fd94a2 100644
--- a/core/apidiff.mk
+++ b/core/apidiff.mk
@@ -58,8 +58,13 @@
     $(full_target): PRIVATE_BOOTCLASSPATH := $(call java-lib-files, android_test_stubs_current)
   else
     ifneq (,$(call has-system-sdk-version,$(LOCAL_SDK_VERSION)))
-      LOCAL_JAVA_LIBRARIES := system_sdk_v$(call get-numeric-sdk-version,$(LOCAL_SDK_VERSION)) $(LOCAL_JAVA_LIBRARIES)
-      $(full_target): PRIVATE_BOOTCLASSPATH := $(call java-lib-files, system_sdk_v$(call get-numeric-sdk-version,$(LOCAL_SDK_VERSION)))
+      ifeq (,$(TARGET_BUILD_APPS))
+        LOCAL_JAVA_LIBRARIES := system_sdk_v$(call get-numeric-sdk-version,$(LOCAL_SDK_VERSION)) $(LOCAL_JAVA_LIBRARIES)
+        $(full_target): PRIVATE_BOOTCLASSPATH := $(call java-lib-files, system_sdk_v$(call get-numeric-sdk-version,$(LOCAL_SDK_VERSION)))
+      else
+        LOCAL_JAVA_LIBRARIES := sdk_v$(LOCAL_SDK_VERSION) $(LOCAL_JAVA_LIBRARIES)
+        $(full_target): PRIVATE_BOOTCLASSPATH := $(call java-lib-files, sdk_v$(LOCAL_SDK_VERSION))
+      endif
     else
       LOCAL_JAVA_LIBRARIES := sdk_v$(LOCAL_SDK_VERSION) $(LOCAL_JAVA_LIBRARIES)
       $(full_target): PRIVATE_BOOTCLASSPATH := $(call java-lib-files, sdk_v$(LOCAL_SDK_VERSION))