do not include stlport headers unless link to it

Change-Id: I8344d270ddb601694b5fef0fa7b22ea437030728
diff --git a/mtp/Android.mk b/mtp/Android.mk
index 38d31ae..57f0ae3 100755
--- a/mtp/Android.mk
+++ b/mtp/Android.mk
@@ -7,7 +7,11 @@
 LOCAL_MODULE := libtwrpmtp
 LOCAL_MODULE_TAGS := optional
 LOCAL_CFLAGS = -D_FILE_OFFSET_BITS=64 -DMTP_DEVICE -DMTP_HOST -fno-strict-aliasing
-LOCAL_C_INCLUDES += $(LOCAL_PATH) bionic external/stlport/stlport frameworks/base/include system/core/include bionic/libc/private/
+LOCAL_C_INCLUDES += $(LOCAL_PATH) bionic frameworks/base/include system/core/include bionic/libc/private/
+ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 23; echo $$?),0)
+    LOCAL_C_INCLUDES += external/stlport/stlport
+endif
+
 LOCAL_SRC_FILES = \
     btree.cpp \
     MtpDataPacket.cpp \
@@ -31,7 +35,7 @@
     node.cpp
 LOCAL_SHARED_LIBRARIES += libz libc libusbhost libstdc++ libdl libcutils libutils libaosprecovery
 
-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++