Remove forced usage of ALPHA version of Jack

Commit 939106dc81a4f850dbf72247062ddcbd537ca413 in prebuilds/sdk
made Carnac the default Jack version.

Bug: 27376034
(cherry picked from commit bf6b6ab7276853eda3891078d8018b5553398374)

Change-Id: Icd3abf957117d970b5e5ff485b4ecbf20ad52ed7
1 file changed