Copy tools needed by host gtests to testcases directory.

Atest requires that everything is in the testcases directory.
The files are not used yet (this is left to follow-up CLs).

Bug: 147819342
Test: check the generated general-tests.zip ("m general-tests")
Change-Id: Ied22a736e81a7cff03641d18bacd829b86a6ef0b
diff --git a/libnativebridge/Android.bp b/libnativebridge/Android.bp
index e05771a..c0f4791 100644
--- a/libnativebridge/Android.bp
+++ b/libnativebridge/Android.bp
@@ -27,7 +27,7 @@
     ],
 }
 
-cc_library {
+art_cc_library {
     name: "libnativebridge",
     defaults: ["libnativebridge-defaults"],
     visibility: [