What Is Bazel Compiler?
What Angular is doing with Bazel Compiler?
The Bazel Complier is a build system used for nearly all software built at Google.
From Angular 6 release, will start having the Bazel compiler support and when you compile the code with Bazel Compiler, you will recompile entire code base, but it compiles only with necessary code.
The Bazel Complier uses advanced local and distributed caching, optimized dependency analysis and parallel execution.
Bazel allows us to break an application into distinct build units. In Angular, build units are defined at the NgModule level.
This means the scope of a build can be as granular as a single NgModule. If a change is internal to an NgModule, only that module needs to be rebuilt.
Angular, Angular Universal, NgRx, and Tsickle all switched to Bazel as the build tool, and ship Bazel-built artefacts to npm.
For more detail kindly refer the