toybox: create getprop symlink on SDK 27

Currently when building for SDK 27 with TW_USE_TOOLBOX,
no getprop symlink is produced. This minor change creates
a symlink for getprop on SDK 27.

Change-Id: I71bd3e0d0525bd0ae51634f52a5749ba0ff58444
diff --git a/toybox/Android.mk b/toybox/Android.mk
index 5b2f32f..c88f360 100644
--- a/toybox/Android.mk
+++ b/toybox/Android.mk
@@ -532,7 +532,7 @@
     vconfig \
     watch \
     xxd
-ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 27; echo $$?),0)
+ifeq ($(shell test $(PLATFORM_SDK_VERSION) -le 27; echo $$?),0)
 ALL_TOOLS += \
     getprop \
     xzcat