My project was managed by pod, and if adding some other libraries will to Libraries folder not to podfile(some library don't include a podspec) , then build project, it will crash of 'React/RCT**.h' file not found.

There is a way to solve this: creating own pod files

But if there is a very complex libraries that I don't know how to create a podspec. How to overcome this?

Environment

Run react-native info in your terminal and paste its contents here.
Environment:
OS: macOS High Sierra 10.13.6
Node: 9.5.0
Yarn: 1.7.0
npm: 5.7.1
Watchman: 4.9.0
Xcode: Xcode 9.4.1 Build version 9F2000
Android Studio: 3.1 AI-173.4720617

Packages: (wanted => installed)
react: 16.0.0 => 16.0.0
react-native: 0.50.1 => 0.50.1