Add MODULE_LICENSE_GPL.. for libcore/ojluni.

This needs a companion makefile that declares a no-op module
so that the build system can leach of its LOCAL_PATH to collect
all subdirectory sources.

bug: 27160386

(cherry picked from commit ac1fc955)

Change-Id: Ie3f1e2e339d4396096c45dc3b659fef5f443fb17