comprehensive-rust/src/chromium/adding-third-party-crates/resolving-problems.md

Resolving Problems

If your build fails, it may be because of a build.rs: programs which do arbitrary things at build time. This is fundamentally at odds with the design of gn and ninja which aim for static, deterministic, build rules to maximize parallelism and repeatability of builds.

Some build.rs actions are automatically supported; others require action:

build script effect	Supported by our gn templates	Work required by you
Checking rustc version to configure features on and off	Yes	None
Checking platform or CPU to configure features on and off	Yes	None
Generating code	Yes	Yes - specify in gnrt_config.toml
Building C/C++	No	Patch around it
Arbitrary other actions	No	Patch around it

Fortunately, most crates don't contain a build script, and fortunately, most build scripts only do the top two actions.