pkg-config and cmake dependency for OSX

OSX also needs pkg-config and cmake dependency. It's not installed per default.

Added 1 new commit:

• 84e93288 - OSX also needs pkg-config and cmake

for cmake. It is required for rugged.

@razer6 Why we need pkg-config?

pkg-config is also needed for rugged. rugged team updated documentation after an issue on GitLab.

See https://github.com/libgit2/rugged#install

Thanks @razer6 !

Had a harddisk head-crash, so perfectly for testing on a clean setup

@razer6 :(