Add installation and packaging targets

[silasmue]

GitLab name: muelless

To reproduce the steps:
Build the docker image:

docker build -t cpack-exercise .

Then start the container, mount the source directory:

sudo docker run --rm -it --mount type=bind,source="$(pwd)",target=/mnt/cpack-exercise cpack-exercise

Change directory to the source code and create a build directory:

cd /mnt/cpack-exercise
mkdir build/
cd build/

Initialize cmake and build the packages:

cmake ..
make package

The last step builds the library, the binary and packs the binary and the library in cpackexample-0.1.0-Linux.tar.gz and a debian, cpackexample_0.1.0_amd64.deb, package that can be installed afterwards with the following command:

apt install ./cpackexample_0.1.0_amd64.deb

When the package is installed successfully you can try the command cpackexample to confirm the installation.

The output of lintian ./cpackexample_0.1.0_amd64.deb should look like this:

lintian ./cpackexample_0.1.0_amd64.deb     
running with root privileges is not recommended!
E: cpackexample: description-contains-invalid-control-statement line 2
E: cpackexample: no-changelog usr/share/doc/cpackexample/changelog.gz (native package)
E: cpackexample: non-standard-toplevel-dir [cpackexamplelib/]             
W: cpackexample: file-in-unusual-dir [cpackexamplelib/fem.hpp]
W: cpackexample: file-in-unusual-dir [cpackexamplelib/filesystem.hpp]
W: cpackexample: file-in-unusual-dir [cpackexamplelib/flatset.hpp]
W: cpackexample: file-in-unusual-dir ... use "--tag-display-limit 0" to see all (or pipe to a file/program)
W: cpackexample: no-manual-page [usr/bin/cpackexample]