Fix build error in old 5.0 tree

Change-Id: I3faa0b6cc964a148dcc1bae7fdeba877fd795cf7
diff --git a/bootloader_message_twrp/Android.mk b/bootloader_message_twrp/Android.mk
index 5a24dc4..e7a3ea0 100644
--- a/bootloader_message_twrp/Android.mk
+++ b/bootloader_message_twrp/Android.mk
@@ -19,7 +19,7 @@
 LOCAL_SRC_FILES := bootloader_message.cpp
 LOCAL_MODULE := libbootloader_message_twrp
 LOCAL_C_INCLUDES += bionic $(LOCAL_PATH)/include
-ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 22; echo $$?),0)
+ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 21; echo $$?),0)
     LOCAL_C_INCLUDES += external/stlport/stlport
     LOCAL_SHARED_LIBRARIES += libstlport
 else