[Android] Change jni_gen_dir to jni_gen_package for jni_generator.

With the old name it was getting relativized which is undesirable. See
bug for more details.

BUG=159133
TBR=ben (nobody really cares about this outside of build/ which cjhopman approved)


Review URL: https://chromiumcodereview.appspot.com/12558005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@186803 0039d316-1c4b-4281-b951-d872f2087c98
16 files changed