do not include stlport headers unless link to it

Change-Id: I8344d270ddb601694b5fef0fa7b22ea437030728
diff --git a/Android.mk b/Android.mk
index 0598796..d54118b 100644
--- a/Android.mk
+++ b/Android.mk
@@ -100,7 +100,10 @@
     system/extras/ext4_utils \
     system/core/adb \
 
-LOCAL_C_INCLUDES += bionic external/stlport/stlport external/openssl/include $(LOCAL_PATH)/libmincrypt/includes
+LOCAL_C_INCLUDES += bionic external/openssl/include $(LOCAL_PATH)/libmincrypt/includes
+ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 23; echo $$?),0)
+    LOCAL_C_INCLUDES += external/stlport/stlport
+endif
 
 LOCAL_STATIC_LIBRARIES :=
 LOCAL_SHARED_LIBRARIES :=
@@ -109,7 +112,7 @@
 LOCAL_SHARED_LIBRARIES += libz libc libcutils libstdc++ libtar libblkid libminuitwrp libminadbd libmtdutils libminzip libaosprecovery
 LOCAL_SHARED_LIBRARIES += libcrecovery
 
-ifeq (,$(filter $(PLATFORM_SDK_VERSION), 23))
+ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 23; echo $$?),0)
     LOCAL_SHARED_LIBRARIES += libstlport
 else
     LOCAL_SHARED_LIBRARIES += libc++