export tradefed .xml templates for tests

Test: xml files are usable by the tradefed rule.
Change-Id: Ifef40fb6cf6a4e5e4be6541dc031628409a710ee
diff --git a/core/BUILD b/core/BUILD
new file mode 100644
index 0000000..3e69e62
--- /dev/null
+++ b/core/BUILD
@@ -0,0 +1,4 @@
+# Export tradefed templates for tests.
+exports_files(
+    glob(["*.xml"]),
+)