use android app's target-sdk (22) also for owncloud lib

maybe should be set via configure, to keep them in-sync

Change-Id: I3747992bb2bbdd88f3668418280bbafc8c998a02

external/owncloud-android-lib/ExternalProject_owncloud_android_lib.mk

@@ -18,7 +18,7 @@ $(call gb_ExternalProject_get_state_target,owncloud_android_lib,build) :
 	$(ICECREAM_RUN) "$(ANT)" \
 		-q \
 		-f build.xml \
-		-Dsdk.dir=$(ANDROID_SDK_HOME) \
+		-Dsdk.dir=$(ANDROID_SDK_HOME) -Dtarget=android-22 \
 		release \
 	)