Google has a multi-year plan to migrate the Android Build system to Bazel. This migration is in early stages, but some changes can be made to current build files to start preparing them for Bazel.
Bazel is Google's open source build system. Bazel projects are described using BUILD files, which are read and analyzed by Bazel into a graph of actions to execute (like compiling a .cc file). After analysis is complete, Bazel executes these actions using tools like clang and javac.
Bazel will provide faster, more reliable builds of AOSP. Bazel should also make it easier to build AOSP in custom configurations.