Add support for ninja build system

Ninja is a widely used and efficient build system. Huge open source projects like LLVM and Chromium use it. Infer doesn't seem to support ninja as of now, therefore losing some decent amount of potential users.

The issue names no files, tests, or entry points. Start by mapping how Infer currently discovers and invokes build systems, then define the supported Ninja workflow and how it can be verified with a representative project. Done means Infer can support Ninja-based projects reliably.

Written by the indexing model from the issue text.