build: Fix order of variable definitions

Fix a use-before-def error in openjdk_java_files.mk

The first time the file is included, the definitions
for openjdk_java_files is not correct because it's missing the stubs.

The file is usually included twice:
once from libcore/Docs.mk and once from libcore/JavaLibrary.mk

The second time it is included those variables will be correct.

libcore/Docs.mk is only included by frameworks/base/Android.mk,
which is absent in some manifests (such as master-art).

As a symptom, core-libart-hostdex make rule would fail to build
on master-art.

Bug: 36902714
Change-Id: Ib8fecdc522814b51ea6cf590dff70a8c05d437da
1 file changed