gitignore: ignore the build directories
Added target to update the sloth cmake modules
Squashed 'cmake/' changes from 941a267..0e62330

0e62330 SlothTools: ignore not existing target in group
cac4612 SlothDoxygen: create dummy target when doxygen not found

git-subtree-dir: cmake
git-subtree-split: 0e6233028c22302f2f6cd60ab67fdde06935f129
Merge commit '3d76e6300b5af7112ab3c8af947c724bf291b95e'