SignApk: perform the whole file signature in a single streaming pass.

Change-Id: Ia29fbc9246254028c75cb57c54cf82ac124c44d0
Allow prebuilt apks & don't build calendar

Change-Id: I2b76f6d5131204b48ac101156f0cd861a3336807
Don't build magic wallpapers
Stop building voice dialer.

Change-Id: Ia079997a2779124765230ba7bba91a6719ad198b