Library used by the Backtrace-unity plugin to send native crashes from game engine to Backtrace.
To build the library select the Backtrace-Unity project and then build it (via CTRL + B command). The build command is going to create the Universal directory in your build dir. In the Universal directory you can also find libraries that were used by lipo to create a static universal "fat" library.
All files necessary to build the library are available in the repository.