[libc] Add documentation for integration tests.

Reviewers: sivachandra

Reviewed By: sivachandra

Subscribers: MaskRay, tschuett, ecnelises, libc-commits

Tags: #libc-project

Differential Revision: https://reviews.llvm.org/D82907

GitOrigin-RevId: aa6ef6fea0f0195779559350b42590b9e251a7d2
1 file changed