Add the keys I used to sign the market version of Superuser.
Use less heap space for dex on 32-bit build hosts

Run dex with -JXmx1024M instead of 2048M if running on a 32-bit host.
Surprisingly this appears to also work for framework and services; if
not, a little fine-tuning will be needed.

This does not change anything for non-32-bit hosts.

Change-Id: I1d87c3e394acc934af6f7770ea54ba265a1df838
Build only modules required by the current product.

Don't build modules_to_check by default.
Instead add "checkbuild" to the command line as a build goal, if you
want to build everything.
We can use the "checkbuild" goal to make sure some build targets on the
build server still build everything.

(cherry-pick of 5a88269ad6ed44fb163f96847954faac21292567.)

Bug: 7253452
Change-Id: I21eb93f3cb430c9531fe41a2f5d7b445c09938b9
Don't build calendar & gallery