Set SDK version for Email to 18.

Change-Id: Ib233193554637506ce5b9cdbe999843b9e5e4ab5
diff --git a/Android.mk b/Android.mk
index d9e28e0..4a9be06 100644
--- a/Android.mk
+++ b/Android.mk
@@ -50,7 +50,7 @@
 
 LOCAL_PROGUARD_FLAG_FILES := proguard.flags $(unified_email_dir)/proguard.flags
 
-LOCAL_SDK_VERSION := current
+LOCAL_SDK_VERSION := 18
 
 include $(BUILD_PACKAGE)