Move libnativebridge headers into the module.

Test: links
Change-Id: I2e19d1ba7845b4b3d3fee934fcb1c90151fd7192
diff --git a/libnativebridge/tests/Android.bp b/libnativebridge/tests/Android.bp
index efd3978..e31dae0 100644
--- a/libnativebridge/tests/Android.bp
+++ b/libnativebridge/tests/Android.bp
@@ -23,6 +23,7 @@
         "-Wextra",
         "-Werror",
     ],
+    header_libs: ["libnativebridge-dummy-headers"],
     cppflags: ["-fvisibility=protected"],
     target: {
         android: {