Bring back squisher as an optional part of the build

Some devices could benefit from the size reduction from running
squisher, so bring it back as an optional part of the build process.

Based on a patch for CM11 originally by Steven Luo (steven676).
Modified by Adrian Perez to fit in the AOSP build tools.

Change-Id: I288f694fd1bf26782e05dcfa797a0569d9fdf9cb