Build libimgdiff as a host only library

Stop building libimgdiff on device because we are only running
patching there.

Test: unit tests pass
Change-Id: I4225c6b52a536617301a64c405e325799a303b40
diff --git a/applypatch/Android.bp b/applypatch/Android.bp
index 620ca6c..64dd38d 100644
--- a/applypatch/Android.bp
+++ b/applypatch/Android.bp
@@ -114,11 +114,9 @@
     ],
 }
 
-cc_library_static {
+cc_library_host_static {
     name: "libimgdiff",
 
-    host_supported: true,
-
     defaults: [
         "applypatch_defaults",
     ],