What problem does this feature solve?

in scripts/build.js

I found that @microsoft/api-extractor was used for the build

If you invoke API Extractor multiple times for a single tsconfig.json environment, this approach also allows you to reuse the same CompilerState object across multiple invocations. This can be a significant performance optimization, since the TypeScript compiler analysis is relatively expensive.

reference

• [1] @microsoft/api-extractor

What does the proposed API look like?

optimize compilation speed

Thanks for the PR but please don't duplicate issues and PRs