Missing pkg-config file doctest.pc

[mortie]

Description

I noticed that most packages for doctest include a doctestConfig.cmake file, but lack a doctest.pc file, probably because the install step of doctest's CMakeLists.txt installs the doctestConfig.cmake file but not the doctest.pc file. This means that Doctest from a system package manager can really only be used if you compile your tests with CMake.

For many Linux distros, this isn't a huge problem because doctest.h ends up in /usr/include/doctest and therefore happens to work, since that's in the default search path and it's a header-only library. However, for macOS with Homebrew and certain Linux distros, pkg-config is vital for even finding the header.

Please consider adding a doctest.pc file.