zlog - zlog is a reliable, high-performance, thread safe, flexible, clear-model, pure C logging library.
openocd - OpenOCD is an open-source tool that allows debugging various ARM devices with GDB using a wide variety of JTAG programmers.
Kconfiglib - Kconfiglib is a Kconfig implementation in Python 2/3. It started out as a helper library, but now has a enough functionality to also work well as a standalone Kconfig implementation (including terminal and GUI menuconfig interfaces and Kconfig extensions).
googletest - googletest is a testing framework developed by the Testing Technology team with Google’s specific requirements and constraints in mind. Whether you work on Linux, Windows, or a Mac, if you write C++ code, googletest can help you. And it supports any kind of tests, not just unit tests.