[Android] Fix regression in binary size

It's introduced by M34 chromium, which include
unwind table for debug trace even for release build.
For chromium case, the debug info will only be
excluded for official build.

Fix this by explicitly disable unwind table for
release build.

TODO: Revert this patch after crosswalk supports
official build also.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1057
Merge pull request #1716 from wang16/no_unwind

[Android] Fix binaries size regression