Build all samples against SDK.

Change-Id: I9ea35c07a7f9d2e2a42d952101e99528fd68fb6c
diff --git a/samples/TtsEngine/Android.mk b/samples/TtsEngine/Android.mk
index 30569ac..a400ef1 100644
--- a/samples/TtsEngine/Android.mk
+++ b/samples/TtsEngine/Android.mk
@@ -7,5 +7,7 @@
 
 LOCAL_PACKAGE_NAME := TtsEngine
 
+LOCAL_SDK_VERSION := current
+
 include $(BUILD_PACKAGE)