Build ganymed-ssh2 against the SDK.

So it can be built in an unbudled branch.

Change-Id: I3b36e196a00f4e2af38960175d4cb3accd0572af
diff --git a/Android.mk b/Android.mk
index 439bf71..2235483 100644
--- a/Android.mk
+++ b/Android.mk
@@ -22,6 +22,8 @@
 
 LOCAL_MODULE_TAGS := optional
 
+LOCAL_SDK_VERSION := 4
+
 LOCAL_MODULE:= ganymed-ssh2
 
 include $(BUILD_STATIC_JAVA_LIBRARY)